Breeding success and chronology of Wood Storks Mycteria americana in northern and central Florida, U.S.A.

The breeding success and chronology of Wood Storks Mycteria americana were studied at eight colonies in northern and central Florida during 1981–1985. Mean ± s.d. clutch size for all colony-years was 3.07 ± 0.56 (n = 2694 nests), with three-egg clutches (72%) most frequent. Mean clutch size among all colonies and years ranged from 2.73 ± 0.55 to 3.41 ± 0.61. Many colonies exhibited significant negative trends in clutch size with, hatching date because of a proportional decrease in four-egg clutches later in the season. Mean colony clutch size was not correlated with nest numbers, nesting density or mean hatching date within most years. Mean ± s.d. number of fledglings for all colonies and years was 1.29 ± 1.16 fledglings per nest (n = 2812 nests). Mean annual fledging rates in colonies ranged from 0 (colony failed) to 2.66 fledglings per nest. Most breeding failure occurred prior to egg hatching, and the second highest mortality occurred between hatching and 2 weeks of age. Four-egg clutches fledged more storks than three-egg clutches, which in turn were more successful than two-egg clutches. However, all clutch sizes showed similar fledgling per egg rates. The seasonal decline in productivity was associated proportionally with smaller clutch sizes later in the breeding season. An increase in mean hatching date was correlated with an increase in latitude. There was greater within-year breeding synchrony among colonies than interyear breeding synchrony within each colony. Breeding synchrony was not correlated with mean hatching date, latitude, longitude, nest numbers or nesting density.     

Laboratory observation of siblicide with hatching asynchrony in an insect with parental provisioning

We report laboratory observation of siblicide with hatching asynchrony in the passalid beetle Cylindrocaulus patalis. Parents construct a breeding gallery in rotten logs and show complex care of offspring, including provisioning. Clutch sizes are extremely small, and only a single offspring is raised in a colony in each breeding season. We introduced field-collected colonies into an artificial gallery and recorded the behaviour of colony members. Eggs hatched at 2- to 10-day intervals in each colony. Fatal fighting invariably occurred among the larvae soon after hatching of the junior larva, and a single larva, usually the senior one, survived.     

Small‐scale spatial variation in evolvability for life‐history traits in the storm petrel

The evolutionary potential in the timing of recruitment and reproduction may be crucial for the ability of populations to buffer against environmental changes, allowing them to avoid unfavourable breeding conditions. The evolution of a trait in a local population is determined by its heritability and selection. In the present study, we performed pedigree‐based quantitative genetic analyses for two life‐history traits (recruiting age and laying date) using population data of the storm petrel over an 18‐year period in two adjacent breeding colonies (only 150 m apart) that share the same environmental conditions. In both traits, natal colony effect was the main source of the phenotypic variation among individuals, and cohort variance for recruitment age and additive genetic variance for laying date were natal colony‐specific. We found significant heritability only in laying date and, more specifically, only in birds born in one of the colonies. The difference in genetic variance between the colonies was statistically significant. Interestingly, selection on earlier breeding birds was detected only in the colony in which heritable variation in laying date was found. Therefore, local evolvability for a life‐history trait may vary within a unexpectedly small spatial scale, through the diversifying natural selection and insulating gene flow. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 439–446.     

Breeding group size, nest position and breeding success in the chinstrap penguin

We studied the effect of breeding group size and nest position on breeding success in the chinstrap penguin (Pygoscelis antarctica). Large subcolonies sited at Vapour Col, Deception Island, had higher breeding success than small subcolonies, which suffered a higher chick mortality than large subcolonies. Hatching date was earlier in large colonies. Relationships were not found between mean hatching date per subcolony and mean chick survival. Chick mortality related to nest position showed no difference between central and peripheral nests in large subcolonies. Central nests hatched earlier than peripheral nests. Nests in large subcolonies, whatever their position, were more successful compared with nests in small subcolonies. Received: 16 April 1997 / Accepted: 12 July 1997     

Boldness and aggressiveness in early and late hatched three-spined sticklebacks Gasterosteus aculeatus

Levels of boldness and the degree of aggressiveness were compared in juvenile three-spined sticklebacks Gasterosteus aculeatus that had hatched early and late in the breeding season. The most striking result found in this study was that early hatched individuals were bolder when exploring a novel environment than were late-hatched individuals. No differences in levels of aggression between early and late hatchlings were found, but a relationship between boldness and aggressiveness was present regardless of hatching date. The implications of these findings are discussed in the light of research on individual variation in behaviour and the development of behavioural syndromes.     

The effects of hatching date on timing of autumn migration in partial migrants – an individual approach

Timing of spring migration and breeding and their interaction with climate change has been widely studied in recent years, but the possible changes in timing of autumn migration have gained less attention. This work focuses on autumn migration and provides the first multi‐species individual‐based study of how hatching date affects the autumn migration date and migration age by using nestling ring data and re‐trappings of the same individuals during the autumn migration at the Hanko Bird Observatory, Finland. We studied three potentially multibrooded passerines (great tit, blue tit and coal tit) and two single‐brooded birds of prey (goshawk, sparrowhawk), all partially migratory short‐distance migrants. Individuals from late broods migrated at a younger age in all tit species and also in hawks the late hatched individuals tended to migrate at a younger age than the early‐hatched individuals. Late‐hatched individuals migrated later than early‐hatched individuals in blue and coal tits, where the latest hatchers represented second brood individuals. Based on our results, the time from hatching to autumn migration is not constant even among individuals of the same population. Our study indicates that climate warming induced advancement of avian breeding may cause changes in the timing of autumn migration through the frequency of second broods.     

NESTING OF THE VILLAGE WEAVER PLOCEUS CUCULLATUS

From August to October 1975, 31 nesting colonies of Village Weavers were identified within an area of 3000 km², south of Lake Chad in Africa. The number of nests and the productivity of each colony were estimated by means of several samplings made during the course of the nesting season. Differences between bush colonies and village colonies are not relevant. The average length of the nesting season is 70 days. In each colony the number of nests increases during the first month and then decreases. The average number of fledging attempts is four per colony, with a period of about ten days from one to another. On a regional scale, breeding periods and fledging attempts are well synchronized. Each nest carries an average of 2.4 eggs and 1.9 young, the difference occurring only at hatching. Due to regional synchronism, the period of most intensive reproductive activity, at which the number of nests reaches its maximum, can be determined.     

Investigating the effects of age‐related spatial structuring on the transmission of a tick‐borne virus in a colonially breeding host

Higher pathogen and parasite transmission is considered a universal cost of colonial breeding due to the physical proximity of colony members. However, this has rarely been tested in natural colonies, which are structured entities, whose members interact with a subset of individuals and differ in their infection histories. We use a population of common guillemots, Uria aalge, infected by a tick‐borne virus, Great Island virus, to explore how age‐related spatial structuring can influence the infection costs borne by different members of a breeding colony. Previous work has shown that the per‐susceptible risk of infection (force of infection) is different for prebreeding (immature) and breeding (adult) guillemots which occupy different areas of the colony. We developed a mathematical model which showed that this difference in infection risk can only be maintained if mixing between these age groups is low. To estimate mixing between age groups, we recorded the movements of 63 individually recognizable, prebreeding guillemots in four different parts of a major colony in the North Sea during the breeding season. Prebreeding guillemots infrequently entered breeding areas (in only 26% of watches), though with marked differences in frequency of entry among individuals and more entries toward the end of the breeding season. Once entered, the proportion of time spent in breeding areas by prebreeding guillemots also varied between different parts of the colony. Our data and model predictions indicate low levels of age‐group mixing, limiting exposure of breeding guillemots to infection. However, they also suggest that prebreeding guillemots have the potential to play an important role in driving infection dynamics. This highlights the sensitivity of breeding colonies to changes in the behavior of their members—a subject of particular importance in the context of global environmental change.     

Seasonal clutch size decline and individual variation in the timing of breeding are related to female body condition in a non-migratory species, the Upland Goose Chloephaga picta leucoptera

Several studies have shown that waterfowl females in good condition lay larger clutches and start egg-laying earlier in a breeding season. However, most of these studies lack corresponding data on individual condition and timing of breeding in different years. We analysed data on clutch size, egg size, hatching date and female body condition of a non-migratory species, the Upland Goose Chloephaga picta leucoptera, recorded in three seasons on New Island, Falkand Islands. We found a strong seasonal decline in both egg and clutch size. Egg size increased with clutch size. The mean egg volume and total clutch volume increased with female body condition and hatching date was earlier for females in higher body condition. Chicks hatched from nests with higher mean egg volume had higher early body condition. We also compared individual females between different study years and found that individual body condition showed a significant repeatability between years, whereas hatching date did not. While female aging did not systematically affect hatching date, females produced clutches that hatched earlier in years of higher body condition. We could thus show for the first time that the frequently reported negative relationship between female condition and hatching date also holds true on an individual basis. To our knowledge, this is the first study on seasonal clutch size decline in sheldgeese and one of a few in waterfowl comparing condition and timing of breeding within individuals between different years.     

Recruitment in the harvester ant, Pogonomyrmex occidentalis: effects of experimental removal

We examined the importance of experimental removal of mature colonies on colony recruitment in the western harvester ant Pogonomyrmex occidentalis. To test the common assumption that established colonies suppress the establishment of new colonies we removed all colonies in ten 0.25 ha plots in 1996 and an additional five plots in 1997 and measured new colony recruitment in 1997, 1998, and 1999. Using a blocked, paired plot design we found that removal of colonies increased new colony recruitment in some areas of the site, but not others. Spatial variation in the importance of established colonies to recruitment was consistent across years; blocks in which density dependence was important in one year exhibited density dependent recruitment in following years. We estimated that in the blocks where recruitment was affected by established colonies, they accounted for less than 10% of the mortality of foundress queens. The increase in the number of new recruits (on average two additional new colonies) was considerably less than the number of colonies removed; average colony density in the removal plots was 14 colonies per 0.25 ha plot. The consistent lack of importance of established colonies to recruitment in one block and the relatively small response to colony removal in the other blocks suggests that the number of new colonies in a year may not be equivalent to the number of deaths of established colonies in that year. Space limitation is an important influence on recruitment in P. occidentalis, but the magnitude of the limitation varies spatially.     

Parental care in Semipalmated Sandpipers Calidris pusilla: brood desertion by females

Although Semipalmated Sandpipers Calidris pusilla are monogamous, with biparental incubation, most females (86–97%) deserted their broods to the care of their mates, 0–11 days (average 6) after their eggs hatched. Males left the brood an average of 8 days later, shortly before or after the chicks fledged. In several instances, females that deserted in one year remained with the chicks the next year, and vice versa. Females deserted chicks at nests that hatched later in the season at an earlier age than those had hatched earlier ( r ²> o.6). Since females appeared to have an energy deficit in at least some years, and suffered higher mortality rates than males during breeding, it is possible that females deserted broods in order to take advantage of better feeding conditions at migratory stopovers in northeastern North America early in the season. There was little evidence of higher nesting success or earlier hatching date in reuniting pairs, although if both members of a pair returned to the breeding area, 80% reunited. Increased survival of their mate may be most advantageous to males in ensuring that they obtain a female the following year.     

Increased lifetime reproductive success of first‐hatched siblings in Common Kestrels Falco tinnunculus

Order of birth has profound consequences on offspring across taxa during development and can have effects on individuals later in life. In birds, differential maternal allocation and investment in their progeny lead to variance in the environmental conditions that offspring experience during growth within the brood. In particular, laying and hatching order have been proposed to influence individual quality during the growing period, but little is known about the fitness consequences that these two factors have for offspring from a lifetime perspective. We explored the effect of laying and hatching order on post‐fledgling survival (measured as recruitment probability) and lifetime reproductive success (LRS) in Common Kestrels Falco tinnunculus, using a long‐term and individual‐based dataset. First‐hatched chicks showed higher survival probability and LRS than their siblings. This effect was not due to body condition of the individuals at adulthood, the quality of their mates or the reproductive outcome compared with later‐hatched individuals. Instead, first‐hatched chicks had a higher recruitment probability. This could be explained by the higher body condition attained by first‐hatched chicks at the end of the nesting period, perhaps due to an enhanced competitive advantage for food over their siblings at the time of hatching. Laying order, in contrast to hatching order, appeared to have little or no effect on LRS. Our results suggest that hatching order within siblings predicts fitness, and that better early‐life conditions during growth experienced by first‐hatched chicks improve first survival and then recruitment, resulting in an enhanced LRS.     

Attendance off breeders and prospectors reflects the quality off colonies in the Kittiwake Rissa tridactyla

Attendance of breeders and prospectors (prebreeders, failed breeders and non-breeding adults) was studied from the time of hatching to the end of the breeding season in parts of two neighbouring Kittiwake Rissa tridactyla colonies in Brittany (France). Many clutches in one subcolony had been predated by a Carrion Crow Corvus corone , leading to a lower breeding success. Attendance of breeders and prospecting activity were greater in the more successful colony, and the number of breeding pairs increased in the following year in this colony only. Local reproductive success and social behaviour contributed to the attraction exerted by a colony. The demographic trend was explained by a performance-based conspecific attraction mechanism, acting through the effect of local reproductive success on recruitment, non-breeding and fidelity. Study of breeding success and prospecting activity allowed both evaluation of the quality of a colony and prediction of local demographic trends for the following year.     

BREEDING OF THE ADÉLIE PENGUIN PYGOSCELIS ADELIAE AT CAPE BIRD

Observations were made during four seasons (1967–68, 1968–69, 1969–70, 1970–71) on the breeding of Adelie Penguins at Cape Bird, Ross Island, Antarctica. Breeding data from individuals were related to date of return, laying date, clutch-size, nest location, and change of mate. Some females consistently laid near the mean date of laying, while others were consistently early or late layers. Laying date may be under direct genetic control, or may reflect feeding ability. The mean clutch-size was smaller in peripheral compared to central nests, and smallest of all in isolated nests. Clutches laid late in the season were smaller than those laid near the peak date, and small, late clutches were laid in peripheral rather than central nests. These differences may reflect age and/or feeding ability. Penguins that are better able to find food will return earlier, obtain central sites, and have larger clutches than those with a lesser ability. The two main causes of egg and chick losses were predation and parental failure. Losses were highest in single-egg clutches, at isolated and peripheral nests, and among eggs laid late in the season. These results may be partly related to the age and experience of the penguins. However, regardless of age, peripheral nesting and late laying were always disadvantageous. The sex ratio of adults in the colonies was 117♂:100♀. This may be explained by the higher mortality of females. Some males could not find partners, but females that did not breed had probably been unable to obtain sufficient food for gonad development. The return of penguins, incidence of non-breeding, adult mortality, clutch-size, and breeding success at Cape Bird were all markedly different in 1968–69 compared to the other three seasons studied. This season was marked by the persistence of sea-ice along the northwestern shores of Ross Island. The low reproductive output in 1968–69 was thought to result from a shortage of food for egg-laying and incubation.     

Sex, age, experience and condition as factors affecting arrival date in prospecting common terns, Sterna hirundo

Several studies have shown that seabird colonies consist to a large extent of young nonbreeders (prospectors). These individuals appear at the colony later in the season than established breeders. The reasons for this late arrival have remained unclear in most cases, mainly because of technical difficulties in collecting sufficient data from nonbreeding individuals. We used a novel transponder system to identify remotely the members of a common tern colony, including nonbreeders, during eight breeding seasons and we combined the system with automatic balances. Ninety-two per cent of prospectors returned for the first time when 2 years old and 88.9% of recruits to the breeding population had spent at least one previous season at the colony as prospectors. In both sexes, most individuals prospected for one season, but more males than females prospected for more than one season, although a higher proportion of females started breeding without a previous prospecting phase. Terns arrived earlier in the season the older they were and the more experience of the colony they had, but experience proved to be more important than age. Prospectors gained about 3 weeks with a previous prospecting season whereas an additional year of age allowed birds to arrive only about 6 days earlier. Prospectors returning later in the season arrived with lower body masses. Males on average arrived earlier at the colony than females. Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour.      

Sociability leads to instability

We present a general stochastic model showing that colonial breeding can lead to complex multi-colony population dynamics when combined with nothing more than (inevitably) imperfect decision-making by individuals. In particular, frequent “switching cascades”—mass movement of individuals between locations from one breeding season to the next—arise naturally from our model, bringing into question the need to invoke a separate, fitness-based explanation for this commonly observed real-world phenomenon. A key component of the model is the development, at the beginning of each breeding season, of a set of colonies, based on sequential choices by individuals about where to breed. Individuals favor the colony they bred in previously, but are also attracted to colonies that are rapidly establishing, and may switch locations. This provides a positive feedback that leads to switching cascades. We examine the effect on the dynamics of individuals’ access to (and ability to act on) information, as well as the overall size of the colony system and of individual colonies. We compare the model’s dynamics to the observed population dynamics of a set of heron and egret breeding colonies in New York Harbor.     

Chick provisioning and breeding success of Adélie penguins at Béchervaise Island over eight successive seasons

Data on foraging trip durations and meal sizes were collected by means of an automated monitoring system from breeding Adélie penguins (Pygoscelis adeliae) at Béchervaise Island over eight breeding seasons, commencing in 1991-92. Significant interannual differences in duration of foraging trips, meal sizes and diet composition were observed. These parameters were correlated with breeding success and fledging masses, and provide useful indicators of food availability during the breeding season. Chicks were particularly vulnerable to a decreased availability of food during the first 3 weeks after hatching.     

Predation by sparrowhawks favours early breeding and small broods in great tits

The selective pressures determining timing of reproduction and brood or litter size in animals remain to be clarified, despite much research. In several detailed studies of birds, selection for an early start of breeding has been demonstrated. Young born early in the season are often assumed to benefit from long experience, high dominance in flocks and/or early settlement in territories. For forest-breeding great tits (Parus major) in Sweden, predation by sparrowhawks (Accipiter nisus) was lower on fledglings hatched early than on those hatched late in the season. Hawk predation may therefore contribute to the higher success of early breeding great tits. Factors favouring early fledglings were (1) increasing food demands over the season in breeding hawks, and (2) hunting by hawks mainly in non-forest habitats when early tit fledglings left their nests. The proportion of fledglings taken was lower in broods of 2-6 than in broods of 7-12, indicating that predation favours small broods. Fledglings in large broods may be more vulnerable due to (1) a higher level of hunger and begging, and (2) higher provisioning rates by parents, which may reveal sites with fledglings to hawks. Territories of sparrowhawks were used as sample units in the statistical analysis, leading to strong inferences about predation at the landscape level.     

Reproductive strategy in orphaned colonies of Myrmica kotokui Forel, the Japanese species of the M. ruginodis complex (Hymenoptera, Formicidae)

Summary: The reproductive strategy between queen-right and orphaned colonies of Myrmica kotokui was compared. The ratio of orphaned colonies reached about 30 percent in the field. Although colony size was significantly smaller in orphaned colonies, the mean body size and mean ovariole length of the workers were significantly larger than those in queen-right colonies. The reproductive individuals in orphaned colonies were also significantly larger than those in queen-right colonies. Only 38.5 % of the orphaned colonies, however, contained eggs during the reproductive season, compared to 100 % of the queen-right colonies. This indicates that worker reproduction under natural conditions is relatively low, even in orphaned colonies.     

Hatching date influences winter habitat occupancy: Examining seasonal interactions across the full annual cycle in a migratory songbird

Birds experience a sequence of critical events during their life cycle, and past events can subsequently determine future performance via carry‐over effects. Events during the non‐breeding season may influence breeding season phenology or productivity. Less is understood about how events during the breeding season affect individuals subsequently in their life cycle. Using stable carbon isotopes, we examined carry‐over effects throughout the annual cycle of prairie warblers (Setophaga discolor), a declining Nearctic–Neotropical migratory passerine bird. In drier winters, juvenile males that hatched earlier at our study site in Massachusetts, USA, occupied wetter, better‐quality winter habitat in the Caribbean, as indicated by depleted carbon isotope signatures. For juveniles that were sampled again as adults, repeatability in isotope signatures indicated similar winter habitat occupancy across years. Thus, hatching date of juvenile males appears to influence lifetime winter habitat occupancy. For adult males, reproductive success did not carry over to influence winter habitat occupancy. We did not find temporally consecutive “domino” effects across the annual cycle (breeding to wintering to breeding) or interseasonal, intergenerational effects. Our finding that a male''s hatching date can have a lasting effect on winter habitat occupancy represents an important contribution to our understanding of seasonal interactions in migratory birds.