Sibling Competition

The age of nestlings was made even in 12 nests of cattle egrets (Bubulcus ibis) by exchanging young chicks or eggs in a breeding colony in Japan. The growth of chicks in such synchronously hatching broods (SHBs) grew almost as fast as first-hatched chicks in 38 control (asynchronously hatching) broods (AHBs). Four last-hatched chicks in AHBs but no chicks in SHBs died of starvation. The frequency of parental nest-visits with food, that of begging food by chicks, and food mass eaten by chicks were greater in SHBs than in AHBs during the first half of the nestling period and similar thereafter. Dominance rank within each SHB was formed through ritualistic fights among siblings. It was correlated with neither growth rates nor winning ratios in food contests, but in some SHBs the subordinate chicks were attacked more frequently by dominant siblings during food contests than in AHBs. The most subordinate chick in one SHB died as a direct result of such attacks. Sibling aggressions were more frequent in SHBs than in AHBs.

Feeding behaviour and sibling competition were observed in nine families of the cattle egret (Bubulcus ibis) from blinds during 1359 nest-h throughout the nestling period. During days 0–19, size differences among siblings were clear; begging behaviour of chicks changed with time. At least one parent always attended the nest. Food boluses regurgitated early within a feeding period were received by senior chicks more often than by juniors. When any two siblings begged for food at the same time, the elder and younger received the first bolus on 65% and 35% of occasions respectively. Between days 20 and 39, the frequency of begging reached a peak. Begging behaviour became intense and stereotyped. The number of boluses received per begging declined rapidly, especially for junior chicks. In large broods, the success rate of begging was lower and fights occurred among siblings, especially among juniors. Out of 256 dyadic fights, the elder sibling won 85, lost one, and tied 171. The youngest chick died in two broods, apparently as the result of these fights (siblicide). No parents interfered in fights among their offspring. After day 40, the frequency of begging decreased gradually and ceased by day 80, No chicks died in the last period, although the frequency of fights in all large broods remained high.

The aim of the study was to estimate some effects on mortality and growth in rabbits. The study was carried out in Slovenian SIKA sire line. In total, 1028 kits of 80 does were included. In the analyses the effects of parity, number of liveborn kits, number of teats, and season of kits birth were analysed. Birth weight was included in the model for mortality, while age was included in the model for growth. Parity, litter siye, teat number and season affected the bodz weights. Body weight varied also according to age. Mortality has changes by litter size, season and initial weight. An average litter size was 8.77 kits born, 8.15 kits born alive and 7.00 kits weaned. The birth to weaning mortality was 14.4% and mortality has steadily declined with age. Average weight up to age 3 days was 72 g and at weaning 959 g. Kits in smaller litters and kits from does with more teats had a higher growth rate. Also kits grow faster in the colder months.Namen študije je bil oceniti mone vplive na r...

Many studies regarding birth order attempt to determine how birth order plays a role in personality development based on factors such as parental treatment, gender, and age gap however, they do not imply the effect of birth order and personality development playing a role within professional work settings. This research aims to explore how birth order plays a role in personality development, more specifically sociability within a specific setting being a professional workspace. In this case a High School was being used as a professional workspace as an ethnographic study was conducted by observing different female employees with four or fewer siblings within their natural work environment and then being asked to answer a short questionnaire. Results found that later born siblings seem to be more agreeable and sociable within professional work environments however, firstborns tend to be less sociable within professional settings due to the tendency to fulfill a "leader" type role. Overall it can be concluded that the work environment specifically, plays a large role in sociability within birth order due to the findings of this study. It's advised in future research to look into different occupations with a larger sample size for more accurate results.

In many species, young solicit food from their parents, which respond by feeding them. Because of the difference in genetic make-up between parents and their offspring and the consequent conflict, this interaction is often studied as a paradigm for the evolution of communication. Existent theoretical models demonstrate that chick signaling and parent responding can be stable if solicitation is a costly signal. The marginal cost of producing stronger signals allows the system to converge to an equilibrium: young beg with intensity that reflects their need, and parents use this information to maximize their own inclusive fitness. However, we show that there is another equilibrium where chicks do not beg and parents’ provisioning effort is optimal with respect to the statistically probable distribution of chicks’ states. Expected fitness for parents and offspring at the nonsignaling equilibrium is higher than at the signaling equilibrium. Because nonsignaling is stable and it is likely...

Parental favoritism is a widely debated phenomenon, with birth order playing a significant role in how parents treat their children. Research suggests that firstborns are often viewed as responsible, mature, and high-achieving, while younger siblings may receive more leniency and emotional support. This paper explores the psychological, cultural, and social influences of birth order favoritism, particularly within Nigerian families. Using Adler's Birth Order Theory, Social Comparison Theory, and Family Systems Theory, the study examines how favoritism impacts sibling relationships, self-esteem, academic performance, and career aspirations. The paper further discusses how Nigerian cultural expectations and traditional parenting styles reinforce or challenge favoritism, influencing family dynamics and child development.

To optimize fitness, organisms may have to trade the number and quality of individual offspring against their own condition and survival. Limiting micronutrients such as antioxidants may be crucial to this trade-off. We investigated whether vitamin E, a major antioxidant in the diet of vertebrates, is limiting to barn swallow (Hirundo rustica) nestlings. We manipulated brood size to alter the intensity of sib-sib competition and supplemented nestlings with two different physiological doses of vitamin E while establishing a control group. Treatment effects were measured on body mass and size, feather growth, T cellmediated immune response and hematocrit. Supplementation with vitamin E at intermediate physiological doses improved nestling mass and condition and feather growth, whereas higher physiological doses did not enhance offspring quality compared to a control treatment. The positive effects of vitamin E on body mass and condition were only detectable from days 6 to 10 when maximum growth rate is attained. Experimental enlargement of broods reduced body mass and size and T cell-mediated immune response only during the late nestling period. The effect of vitamin E supplementation did not depend on brood size manipulation, as revealed by the nonsignificant statistical interaction. This result contradicts the hypothesis that availability of vitamin E depends on intrabrood competition and instead suggests that it depends on concentration of vitamin E in the insect prey of swallows. Thus, antioxidants may be available in limited amounts to barn swallow nestlings and such limitation affects growth. In addition, present results confirm that barn swallow parents trade progeny number against growth and immunity of individual offspring.

In this paper we present a few behavioral features regarding the piglets’ birth process, the sow and piglets bonding, piglets investigative behaviour and care application behaviour of piglets. As biologic materials, we used piglets in extensive raising systems belonging to some households in Varfurile, County of Arad. Parturition may take up to 2-3 until 12 hours or longer; the total duration of parturition is different from race to race and from animal to animal, usually being longer with primiparous sows and shorter with multiparous sows. Most times farrowing takes place at night or in the evening. For a sow farrowing in decubitus position, expulsion interval between two piglets is between 10 and 30 minutes. At 10-20 minutes after the parturition, the piglets start to look for the sow’s nipples. Fore nipples are preferred because they are rich in milk. After farrowing, sows allow their piglets to suckle and are careful not to crush them. Most of a sow’s piglets begin to suckle and...

Sibling competition has been shown to affect overall growth rates in birds. However, growth consists on the coordinated development of a multitude of structures, and there is ample scope for developmental plasticity and trade-offs among these structures. We would expect that the growth of structures that are used in sibling competition, such as the gape of altricial nestlings, should be prioritized under intense competition. We conducted an experiment in the spotless starling (Sturnus unicolor), cross-fostering nestlings to nests with different levels of sibling competition. We predicted that nestlings subjected to higher levels of sibling competition should develop larger gapes than control birds. We found that, halfway through the nestling period, overall size (a composite index of mass, wing, tarsus and bill) was reduced in nests with intense sibling competition, whereas gape width remained unaffected. At the end of the nestling period, experimental nestlings had wider gapes than...

Nestling begging in passerine birds is a complex behaviour that is shaped by a multitude of ecological factors and could be physiologically mediated by varying levels of steroid hormones. Previous research has shown links between sibling competition and testosterone and corticosterone in several bird species. The spotless starling (Sturnus unicolor) is a medium sized passerine in which nestlings compete intensively for resources, often resulting in marked size hierarchies that can have profound effects on their fitness. We tested the hypothesis that an increase in sibling competition levels would result in increases in testosterone and corticosterone in this species. To this end we conducted a brood size manipulation, creating small, medium and large broods. This manipulation had the expected effect on morphology: nestling size and mass decreased with increasing brood size. Androgen levels varied in response to brood size manipulation but, contrary to expectations, the largest concentrations were found in reduced brood sizes. Corticosterone levels increased with increasing brood size, but this effect disappeared when we corrected for the time taken to process nestlings. Cell-mediated immune response was found to decrease with increasing brood size and testosterone levels. The results suggest that the proposed link between testosterone and corticosterone and sibling competition does not hold in this species, and underlines the diversity of species-specific responsiveness to steroids.

Begging in avian nestlings is a highly conspicuous behavior with important implications for the study of parent-offspring conflict. In some species, nestlings also call for long bouts in the absence of parents, and it has been proposed that this behavior is used by nestlings as a means of negotiating access to food. We studied this phenomenon in the spotless starling (Sturnus unicolor). We found that parent-absent calls were acoustically distinct from parent-present calls. Observations showed that the probability of parent-absent begging increased with nestling age and brood size, whereas it decreased with increasing body condition. This result was confirmed by an experiment that showed that nestlings produced higher parent-absent begging rates when food deprived than when satiated. Finally, we carried out a playback experiment to test the reaction of nestlings to parent-absent begging by fellow nestlings. Principle components analyses yielded 2 independent components of begging: 1) a general begging component and 2) a second factor that measures the relative contribution of communicative begging over competitive begging. Nestlings exposed to playback decreased their general begging levels and simultaneously increased the relative contribution of communicative over competitive begging. This behavior may favor needy nestlings to obtain impending feedings while keeping high levels of food solicitation from parents and is consistent with a cooperative strategy among nestlings. Future research should consider the actual response of parents to these signals.

We tested various predictions based on Sulloway's [Born to rebel: birth order, family dynamics, and creative lives. New York: Pantheon, 1996] theory of family relations, using questionnaires completed by 2024 participants from Austria, Germany, Israel, Norway, Russia, and Spain, each of whom had at least one sibling. The parents' most favored child tended to be the lastborn sibling. The rebel of the family tended to be a laterborn, and rebels tended to feel less close to their parents. In sibships of two, firstborns named a parent as the person to whom they were closest more often than did lastborns; in sibships of three or more, middleborns were the least likely to name their mother, but were more likely than firstborns and lastborns to name their father or a sibling. However, these quadratic effects on closeness to parents occurred only in sibships in which mothers were relatively old at the time of participant's birth. Sex differences, but not birth order differences, were found in the tendency to choose parents for emotional support, with women scoring higher than men. Our study demonstrates the robustness of birth order differences in samples from diverse countries and emphasizes that these

It has been suggested that nestlings use begging to increase their share of parental resources at the expense of current or future siblings. There is ample evidence that siblings compete over food with nestmates by begging, but only short-term eects of begging on parental provisioning rates have been shown. In this study, we use a new experimental design to demonstrate that pied¯ycatcher (Ficedula hypoleuca) nestlings that beg more are able to increase parental provisioning rates over the major part of the nestling period, thus potentially competing with future siblings. Parents were marked with microchips so that additional begging sounds could be played back when one of the parents visited the nest. By playing back begging sounds consistently at either male or female visits, a sex dierence in provisioning rate that lasted for the major part of the nestling period was induced. If each parent independently adjusts its eort to the begging intensity of nestlings, begging may also be the proximate control mechanism for the sexual division of labour.

It has been suggested that nestlings use begging to increase their share of parental resources at the expense of current or future siblings. There is ample evidence that siblings compete over food with nestmates by begging, but only short-term eects of begging on parental provisioning rates have been shown. In this study, we use a new experimental design to demonstrate that pied¯ycatcher (Ficedula hypoleuca) nestlings that beg more are able to increase parental provisioning rates over the major part of the nestling period, thus potentially competing with future siblings. Parents were marked with microchips so that additional begging sounds could be played back when one of the parents visited the nest. By playing back begging sounds consistently at either male or female visits, a sex dierence in provisioning rate that lasted for the major part of the nestling period was induced. If each parent independently adjusts its eort to the begging intensity of nestlings, begging may also be the proximate control mechanism for the sexual division of labour.

The effect of low nesting density caused by the fragmentation of nesting biotopes due to seasonal flooding on the development of aggressive behavior and on growth of black headed gull chicks was investi gated. An analysis of the behavior of birds nesting with different densities showed that contacts with neigh boring broods were less frequent in chicks from more sparsely distributed nests, while aggressive behavior could be observed in these broods earlier and more often than in their peers from the nests located in more densely populated areas. By testing the parent birds using a standard stimulus of territorial behavior-a remotely controlled stuffed gull-we found that the hosts of widely spaced nests reacted more aggressively but left the clutches less frequently than their neighbors that nested more densely. On average, the chicks from the sparsely distributed broods grew faster and the daily increment of the skull size of the chicks correlated inversely with the frequency of parental visits. We suppose that in the case of the seasonal decrease of nesting grounds, the offspring of more aggressive young couples nesting in the most sparsely populated areas had an advantage in the development probably due to the maternal influence on the composition of the eggs. According to our data, in the conditions of low density nesting, the parental influence on the growth of chicks and development of their aggressive behavior prevailed over the possible developing effect of the social expe rience.

Despite the ubiquity of energetic costs as an explanation for behavioural evolution, the proximate basis of these costs is often unclear. One candidate that predictably regulates energetic expenditure in insects is the lipid metabolism pathway, which is used in behavioural activities such as flight. Here, we investigated lipid metabolism and its role in parental behaviour of males and females in two species of burying beetle, Nicrophorus orbicollis and Nicrophorus vespilloides, which provide pre-hatching care by burying and preparing vertebrate carcasses before larvae arrive, and then post-hatching care by directly regurgitating food to begging offspring. We took two approaches: first, we investigated changes in the lipid stores of parenting beetles during pre-hatching and post-hatching care by measuring triglyceride concentration, compared to beetles not involved in care. Second, we quantified expression of the lipid transporter gene apolipophorin-III (apoLp-III) in these three behavioural states. Females and males of both species were similar in triglyceride use, but there were species differences. We observed a loss of triglycerides during pre-hatching but not post-hatching care in N. vespilloides, but no change in triglycerides during either pre-or post-hatching care in N. orbicollis. There were both species and sex differences in apoLp-III expression. Expression decreased during caring in both male and female N. orbicollis, and male N. vespilloides, but only decreased in female N. vespilloides providing post-hatching care. This roughly corresponded to changes in triglyceride abundance. These results indicate that either parental care is not energetically costly or, more likely, that lipid metabolism plays only a partial role in regulating energetic expenditure during Nicrophorus parental care. We suggest that the energy source used varies, perhaps between species but certainly across behavioural states. Furthermore, our results suggest that ApoLp-III may provide an alternate behavioural or immune function during parental care besides its canonical role as a lipid transporter.

Knowledge of animal dispersal patterns is of great importance for the conservation and maintenance of natural populations. We here analyze juvenile dispersal of the poorly studied Black-shouldered Kite (Elanus caeruleus) monitored in southwestern Spain in an ongoing long-term study initiated in 2003. The European population of Black-shouldered kites is thought to be a recent one funded by colonizing African birds, as no kites have been found in the European fossil record, and the breeding population has progressively expanded to the North in the late 20th and 21st centuries. We obtained information on movements behavior during dispersal from 47 juveniles Kites after marking 384 nestlings with wing tags and three nestlings with radio transmitter. We have tested two competing hypotheses (i.e., the Resources Competition Hypothesis and the Wandering Hypothesis (WH)) that may explain the leptokurtic distribution of the natal dispersal distance in Elanus. After independence, juvenile fema...

Does timing of breeding matter less where the grass is greener? Seasonal declines in breeding performance differ between regions in an Endangered endemic raptor……………………………………………………………………………………………..27 Chapter 2: Is the Black Harrier Circus maurus a specialist predator? Assessing the diet of an Endangered raptor species endemic to southern Africa…………………...........57 Chapter 3: Regional and temporal variations in diet and provisioning rates suggests weather limits prey availability for an Endangered avian predator………………..71 Chapter 4: Blood concentrations of PCBs and DDTs in an avian predator endemic to southern Africa: associations with habitat, density of electric transformers and diet………………………………………………………………………………………………………………102 Chapter 5: Pollutants and diet influence carotenoid levels and integument coloration in nestlings of an endangered raptor…………………………………………………………..….134 General Synthesis……………………………………………………………………………………….158 References………………………………………………………………………………………………….172 vi Acknowledgements There are so many people to thank! Those who were physically present, and others that, despite the geographical distances, have always been there supporting me in achieving this incredible goal. A sincere thanks to all of you. Firstly, I am extremely thankful to Dr. Rob E. Simmons for answering the email I sent him back in April, 2012, when I was still looking for PhD opportunities. Rob gave me the incredible chance to come to South Africa in September 2012, when I started doing fieldwork within his Black Harrier research project. I still remember the first time I saw this majestic bird of prey flying over the flowery Fynbos vegetation at the Silverstroom study site… An adult male was carrying prey in its yellow tarsi when, suddenly, after listening to this typical sharp food call, a wonderful female appeared from nowhere, flying towards him. A few seconds later, an incredible food pass between both creatures took place, and at that moment I stayed there, completely amazed by the beauty of the spectacle that just happened before me. What an incredible way to start what would become this extraordinary journey of more than 4 years! Rob, you taught me almost everything I know now about Black Harriers, from how to find a nest in very dense vegetation and harsh conditions, to how read an individual's behaviour and interpret its signs-I have learned an incredible amount during these years. I am very thankful for that! I am also very grateful for having been able to use all the precious data you have been collecting since 2000 and for all of your hard work correcting drafts and improving my English! I am looking forward to our future collaborations. To Beatriz Arroyo and François Mougeot-I have so many things to say, that I don't even know where to begin! What an outstanding Spanish-French couple! You taught me an incredible amount of things, from helping me conceive and implement diverse fieldwork technics and tricks, how to efficiently catch adult Black Harriers, how to analyse data and ask yourself the right questions, bettered my English in writing papers, how to bring confidence when giving a talk at a conference, and how to take a step back and cool down in difficult and challenging situations. Thank you so much for your hard work correcting drafts, for always being so available and responsive, for spending the many hours skyping between Cape Town and Ciudad Real, and for the stimulating chats we have had around a drink, talking in our favourite language, "Frenchspanglish". I am definitely looking forward to our future projects! I am also very grateful for letting me stay at your house when I was visiting Ciudad Real and for making me feel, since the very beginning, that I was part of your family. I also want to thank Gaelle and Yan, their two kids, who I have seen growing up and evolving over the last four years-thanks for the many fun moments and laughs! To Prof. Graham Cumming, who was initially my official supervisor. Thank you for supporting my research at the very beginning and for the economic support you provided! Dr. Arjun Amar joined as my official supervisor in 2015, after Graham left the Fitz towards his new Australian adventures. Thank you for the constructive chats and for improving many pieces of my work! To Peter Ryan, thanks for the chats we had about pollutants and contaminants and for being such an amazing director. To Susie Cunningham, thank you for your kindness, for the many chats about life and research, for staying calm and diplomatic in tough situations with a positive attitude! I felt very privileged to have been your office mate for more than two years! * log transformed § square-root transformed

Male Australian brush-turkeys, AUctura lathami, provide all parental care by building and tending large incubation mounds. Females visit and lay eggs in the mounds of several males sequentially, but they provide no parental care after laying. Because males and females meet only briefly at mounds to copulate and lay, males have no obvious means of ensuring paternity. I used DNA fingerprinting techniques to determine paternity for 65 brush-turkey rhirfct Eighteen chicks (27.7%) did not match the mound-tending male. Some of these paternity exclusions were evidently caused by females switching rapidly from one mound to another, but the majority (23.1% of eggs) appeared to result from females copulating with males other than the one in whose mound they were currently laying. However, the frequency of these copulations (43%) was much lower than the estimated frequency with which they fertilized eggs, perhaps because their timing during the ovulatory cycle differed relative to most other copulations. The percentage of eggs excluded in paternity analyses ranged from 20.0% to 43.8% for individual males but did not appear to affect male parental care. Several factors favor male parental care regardless of paternity. Males can accommodate eggs from several females in one mound, which increases the opportunities for additional roarings without increasing the cost of parental care. In addition, paternity appears to be unpredictable and hard to assess, and a facultative reduction in care would be difficult without abandoning a mound entirely.

The brood reduction hypothesis for asynchronous hatching was tested for the jackass penguin, Spheniscus demersus, by comparing the reproductive success of two-chick broods with different degrees of asynchrony, and by identifying the behavioural basis of competitive asymmetries between siblings. By interchanging newly hatched chicks between nests, broods of synchronous and extended asynchronous siblings were created. There was no significant difference in fledging success between unmanipulated normal asynchronous (mean number of chicks per brood = 1.14) and synchronous (1 "44) broods; however, extended asynchronous (0"6) broods lost significantly more chicks than normal asynchronous ones. Last-hatched chicks in normal asynchronous broods were more likely to die than their siblings, and all last-hatched chicks in extended asynchronous broods failed to fledge. Chicks in normal asynchronous broods were not significantly heavier at fledging, but did attain higher maximum body weights before fledging, and fledged sooner than chicks in synchronous broods. This appeared to be due to higher begging success and lower sibling competition during feeding by asynchronous chicks. In terms of chick survival, the brood reduction hypothesis does not provide an explanation for hatching asynchrony in the jackass penguin. Asynchrony may, however, provide an advantage with respect to fledgling quality and postfledging survival, as predicted by extensions of both the brood reduction and the sibling rivalry reduction hypotheses.

Altricial mammals typically lack the physiological capacity to thermoregulate independently during the early postnatal period, and in litter-bearing species the young benefit strongly from huddling together with their litter siblings. Such litter huddles are highly dynamic systems, often characterized by competition for energetically favorable, central positions. In the present study, carried out in domestic rabbits Oryctolagus cuniculus, we asked whether individual differences in body mass affect changes in body temperature during changes in the position within the huddle. We predicted that pups with relatively lower body mass should be more affected by such changes arising from huddle dynamics in comparison to heavier ones. Changes in pups' maximum body surface temperature (determined by infrared thermography) were significantly affected by changes in the number of their neighbors in the litter huddle, and indeed these temperature changes largely depended on the pups' body mass relative to their litter siblings. Lighter pups showed significant increases in their maximum body surface temperature when their number of huddling partners increased by one or two siblings whereas pups with intermediate or heavier body mass did not show such significant increases in maximum body temperature when experiencing such changes. A similar pattern was found with respect to average body surface temperature. This strong link between changes in the number of huddling partners and body surface temperature in lighter pups might, on the one hand, arise from a higher vulnerability of such pups due to their less favorable body surface area-to-volume ratio. On the other hand, as lighter pups generally had fewer neighbors than heavier ones and thus typically a comparatively smaller body surface in contact with siblings, they potentially had more to gain from increasing their number of neighbors. The present findings might help to understand how individual differences in body mass within a litter lead to the

In altricial, litter-bearing species, huddling together with siblings during early life is a vital strategy to maintain a sufficiently high and stable body temperature. In this context, individual differences in huddling behavior within litters have been emphasized, as pups regularly occupying more central positions have relatively higher body temperatures, have quicker access to the mother's nipples during nursing, and consequently show greater growth. However, it is not known whether such positive effects of a central litter huddle position on within-litter differences in growth translate into an overall higher weaning mass, taking into account strong contributors to among-litter growth variation, such as litter size and maternal parity. We used path analysis to investigate causal relations among these variables, based on data from 150 domestic rabbit pups from 24 litters. Our results confirmed positive, indirect effects of pups' central litter huddle position on within-litter differences in early growth. This positive effect of a central litter huddle position also contributed to explaining a significant part of the overall across-litter variance in weaning body mass, apparent even when controlling for the direct negative effect of litter size, the direct positive effects of birth mass, and the lower offspring growth in primiparous compared to multiparous mothers. Thus, the results underline the key role of individual differences in litter huddle position in shaping within-litter but also overall variation in early growth. This might constitute an important mechanism accounting for how the positive association between body mass at birth and early growth is mediated in altricial, polytocous mammals. Significance statement Huddling together with siblings during early life saves energy and thus can contribute to early growth in small, altricial mammals. However, this strategy can also lead to individual differences within the litter, as heavier pups typically occupy energetically more favorable positions in the center of the huddle. In our study, we show and compare the different causal pathways underlying this effect. Most importantly, our analysis shows that advantages in early growth arising from a more central position in the litter huddle are also apparent when comparing pups across all litters-even though there is typically a notable variation in growth among different litters, for example due to litter size and maternal (parity) effects. In conclusion, the results underline the key role of sibling interactions within the litter in shaping differences in early growth, with potential fitness consequences during later life.

Breeding of spotted shags at Whitewash Head, Banks Peninsula, was studied in 1970 and 1971. The Whitewash Head colony consisted of a central area of breeding shags and peripheral areas largely of non-breeding birds. Male shags selected nest sites on ledges before pairing. Bath birds built the nest, and copulation took place at this time. Egg-laying started about the same time both years but varied within the colony. Most clutches were of three eggs and were laid within seven days. Incubation took from 28 to 31 days and was shared by mates. Development of the chick is described in detail and measurements of growth rates discussed. Nestlings were attended constantly until about 30 days old and were fed about four times daily by both parents. Clutch size and nestling mortality is discussed briefly. Nestlings fledged and left their nests when about 63 days old. No predation of shags occurred but red-billed gulls worried adults feeding chicks to obtain food. A method for ageing nestlings by measurements is given.

Nestling begging behavior in the context of parent-offspring communication has long been seen as a signal by which nestlings solicit care. Begging is a multi-component signal in which both acoustic and visual components are usually important; however, the present knowledge about the specific behavioral features that convey the information is still poor. The aim of this study was to examine how information on nestling's need is encoded in the begging calls given by nestling Spanish Sparrows (Passer hispaniolensis). Nestlings were individually submitted to a food-deprivation period and stimulated to beg at regular intervals within that period, and their acoustic reactions were studied. Spanish Sparrow nestlings increased their response to simulated parental visits in reaction to increasing food-deprivation periods. Results also confirmed that information on nestling need might be encoded in variables of calling behavior. The variables important to convey such information are the initial call rate (20 s rate), duration of the begging bout, call amplitude, and call high frequency. As food-deprivation periods increased, nestlings begged more frequently, extended the calling bout, increased the call amplitude, and used higher frequencies. During the deprivation period, nestlings did not change their call latency, call duration, or relative peak time. The study also found that despite expectations, lower-condition nestlings did not beg more frequently during the experiment than their higher-condition siblings. Overall, results support the view of begging as a reliable signal, namely that begging should reflect a nestling's need, and that only some call features might encode information about need. http://zoolstud.sinica.edu.tw/Journals/48.5/587.pdf

Piglet suckling behaviour has been extensively studied, but surprisingly, there are not many studies that specifically consider body weight and sex in this context. These two basic individual characteristics have been considered more as supporting data but not as main factors. Therefore, the objective of the present research was to examine the effect body weight on suckling behaviour of piglets during lactation separately by sex. The study comprised 14 litters with a total of 158 piglets (85 male, 73 female, litter size 6−15 piglets). Suckling behaviour was described in terms of suckling position (the teat at which the piglet suckled during suckling), suckling territory (the range two outermost suckling positions of the piglet encompasses) and suckling stability (the tendency to suckle successively at the same position), and was observed in six periods: 0−3, 4−7, 8−10, 11−14, 15−21 and 22−32 days of age. In each period, piglets were also weighed. The udder was divided into three areas: anterior (1st-2nd teat pair), middle (3rd-5th teat pair) and posterior (6th-8th teat pair). Body weight affected suckling behaviour differently in male and female piglets (i.e., all traits in females, suckling stability only in males). The relative body weight of females decreased significantly from the anterior towards the posterior part. Heavy females (but not males) suckled considerably more frequently on the anterior area. Heavier piglets (male and female) established more stable suckling order. Suckling territory of males was quite large, but did not differ among body weight classes. Interestingly, light females visited significantly larger suckling territory than heavy females. The present results fill a gap in the otherwise broad knowledge of pig suckling behaviour, which is of great importance for litter management during lactation, especially when cross-fostering is implemented. In this context, knowledge of the detailed role of sex and body weight is of particular importance because breeders rely mainly on basic body traits when managing litters.

Adjusting foraging strategies is a common phenomenon within groups of animals competing for the same resource. In polytocous mammals, neonates concurrently compete for limited milk and alternate between two foraging (suckling) strategies: adaptable exploratory foraging with random sampling of teats, and ordered foraging with a tendency towards exploiting a particular suckling position. Some theoretical (game theory) models have shown that weaker siblings in particular benefit from foraging specialization (suckling order). Neonate piglets establish a well-defined suckling order that develops gradually and fluctuates throughout the lactation period, implying the existence of inter-individual differences in foraging strategies. We therefore analyzed suckling behavior in pigs to determine whether one foraging strategy was more beneficial to neonates in terms of their body weight and foraging environment. We found that intermediate and heavy littermates tended to adjust their suckling strategy according to the foraging environment; however, the selected foraging strategy did not affect their overall growth performance. Lighter individuals that consumed significantly less milk did not greatly alternate their foraging strategy according to the foraging environment, but their growth rate was significantly higher whenever they performed less-exploratory foraging behavior. Although suckling order appeared to be a relatively stable behavioral phenotype, it was beneficial exclusively for weaklings. These results confirm theoretical predictions and indicate that specializing in a suckling position is a beneficial strategy for weaker, light neonates. These findings suggest that physically weaker neonates might have driven the evolution of neonatal foraging specialization.

Göttingen minipig (GMP) has gained importance as model animal in human medicine. However, little is known about the suckling behaviour of GMP. Suckling is considered as a fundamental behavioural trait in mammals, most important for development and survival of the individual. Understanding its development and changes due to artificial selection is important when planning selection on reproductive traits in sows. GMP is a highly valuable model for studying the suckling behaviour in the pig, because its key features are intermediate between commercial breeds (CB) and wild boar (WB), namely, similar teat number as CB, similar litter size as WB and balanced muscularity of extremities. We compared the suckling behaviour of GMP and CB based on measures of suckling stability (the probability of consecutive sucklings on the same suckling position), suckling ranges (number of teat pairs in the range of the outermost teat pairs that piglets occupied) and piglets' distribution along the udder by use of the MDEmodel (effect of geometric constraints, normally expressed as a hump-shaped distribution of organisms). We also incorporated published date on suckling preferences of WB piglets. Our study revealed alterations of suckling behaviour in piglets, wherein GMP showed intermediate suckling strategies (i.e. suckling ranges). However, there appeared to be a certain degree of behavioural conservatism. Domestic piglets maintained the tendency to prefer abdominal (middle) teats, which are anatomically posterior in WB and preferred by wild piglets. It can be suggested, that this general tendency seen in domestic piglets (GMP and CB), is not generated by geometric constraints (mid-domain effect), but appears to originate from the wild ancestor. Results of the present study suggest that the selection of CB for increasing litter size and higher number of teats might have led to imbalances between suckling behaviour, teat number and udder space availability.

Cross-fostering (C-F) is a standard procedure in the rearing of piglets which involves the relocation of piglets from biological to the foster mother/litter. Piglet's integration into the new suckling environment is of crucial importance and depends on many factors that make C-F implementation a significant challenge for pig-breeders. Here, we experimentally cross-fostered piglets of different age and body weight between 20 litters of different sizes. The study aimed to determine the impact of age, body weight, and litter size asymmetry between C-F piglets/litters on the fostered piglets suckling activity immediately after C-F. It appeared that body weight did not have any impact on the integration of piglets into the new suckling environment. Besides, we found that piglets which were older (for 1 to 1.5 day on average) than their foster peers more likely succeed to suckled successfully in the first two post-C-F suckling events (p < 0.01), while piglets transferred into older litter (for 2 days on average) were significantly non-active in suckling. Furthermore, and contrary to our prediction, piglets transferred into the litter of the same or slightly larger size than their original litter succeed to suckled successfully in the first two post-C-F suckling events (p < 0.05), with an evident passiveness of piglets transferred into the smaller litter (with 1 piglet less on average, p < 0.05). We suggested that the level of suckling order development (suckling stability/teat fidelity) dictates piglet integration into the new suckling environment. Accordingly, we found postponed or even prevented integration when piglets were transferred into the smaller or older litter, wherein the suckling order is supposed to be more robust. It appears that some of the widely used C-F methodologies (e.g., litter equalization) might compromise piglets' welfare. We, therefore, suggest reconsidering the use of existing C-F methods.

Parental investment theory proposes two non-mutually exclusive hypotheses to explain variation in anti-predator behaviour in relation to the age of offspring: the "reproductive value of offspring" hypothesis and the "harm to offspring" hypothesis. The relative importance of the two factors underlying the hypotheses, reproductive value and harm, may change depending on environmental conditions such as food availability. To test the relative importance of the two hypotheses under different food conditions, we conducted a supplementary feeding experiment in red kite (Milvus milvus) breeding pairs and used a live eagle owl (Bubo bubo) as decoy nest predator to trigger anti-predator behaviour. We used time-to-capture in mist nets mounted next to the decoy predator as proxy for mobbing intensity. Under natural food conditions we found a nearly constant mobbing intensity throughout the entire nestling period. However, under food-enhanced conditions mobbing intensity was reduced in parents with young nestlings and increased in parents with old nestlings. These results suggest greater importance of the "reproductive value of offspring" hypothesis in situations of favourable food availability. Moreover, mobbing intensity depended on brood size and weather conditions. The results suggest that parental anti-predator investment increases with the reproductive value of the brood under favourable breeding conditions, but that this pattern is adjusted to the current context, including the vulnerability of the brood and environmental conditions.

Human recreational activities increase worldwide in space and frequency leading to higher rates of encounter between humans and wild animals. Because wildlife often perceive humans as predators, this increase in human disturbance may have negative consequences for the individuals and also for the viability of populations. Up to now, experiments on the effects of human disturbance on wildlife have mainly focused on individual behavioral and stress-physiological reactions, on breeding success, and on survival. However, the effects on other physiological parameters and trans-generational effects remain poorly understood. We used a low-intensity experimental disturbance in the field to explore the impacts of human disturbance on telomere length in great tit (Parus major) populations and found a clear effect of disturbance on telomere length. Adult males, but not females, in disturbed plots showed shorter telomere lengths when compared to control plot. Moreover, variation in telomere len...