Future Breeding Success Research Articles

Penguin colonies and weather in Admiralty Bay in a colder year

Climate change will affect many species in the next decades. Antarctic seabirds are of special concern given their dependence on the balance of sea ice-caps. The objective of this paper is to present information about weather and penguin colonies in the last extreme cold summer of 2009/2010. We verified the average temperature in November (beginning of seabird breeding) which was lower than for most years since 1987 with a slight tendency to decline, and thus the number of snow days was also high in relation to the period average, with a tendency to increase in time. The Adelie Penguin has the biggest colony area followed by Chinstrap Penguin, while Gentoo Penguin has the smallest area. As seabirds breed on ice-free areas, the joint effect of lower temperatures and enhanced precipitation in Spring can affect habitat availability for nesting, potentially disrupting reproduction timing and the future breeding population and success.

Breeding behaviour of the platypus (Ornithorhynchus anatinus) in captivity

Breeding platypuses (Ornithorhynchus anatinus) in captivity had proved difficult until the last 10 years but with improvements in husbandry and a greater understanding of platypus biology there have been seven successes at two institutions since 1998. This study, using closed circuit video monitoring, took place between 2001 and 2007 at Taronga Zoo and covered three breeding successes with one female in 2002/03, 2004/05 and 2005/06. Results have revealed a consistency of behavioural patterns, which accurately predicted breeding events, mating, burrow construction, subsequent denning period and emergence of young. The female platypus had a receptive period of 4–6 days in the spring of each year, during which her behaviour changed from avoidance to initiating contact with the male. After mating she immediately commenced burrow preparation, ending with a 3–5-day intense period of collecting wet nesting material before retiring to the burrow to lay. The gestation period was estimated at 15–21 days and incubation at less than 12 days. A suckling period of 114–127 days followed, with the frequency of maternal burrow visits and length of stay decreasing as the juveniles grew. Juveniles emerged 133 ± 4 days after retirement. This study provides new and important information about breeding behaviour in this species and will contribute to future breeding success of platypus in captivity.

Habitat utilisation during staging affects body condition in a long distance migrant, Branta bernicla hrota: potential impacts on fitness?

There is considerable evidence to suggest that an animal's ability to access the appropriate resources at one time of year may profoundly restrict its performance at another. For migrants, wintering and breeding periods are often connected by refuelling or staging periods, critical (particularly for females) in attaining the body reserves required to ensure successful breeding. However in many instances there are differences in the extent to which different individuals gain access to the highest quality resources. Here we demonstrate how body condition in brent geese Branta bernicla hrota, during spring staging is related to differences in marine and terrestrial habitat utilisation (inferred from stable isotope analysis). Female birds with high fat scores feed to a greater extent on marine resources. Body mass and condition are also higher in individuals utilising more marine resources. Given that body mass at spring staging is correlated with reproductive success, the extent of marine habitat maybe critical to this population. Combining this with data from previous studies of dark‐bellied brent geese Branta bernicla bernicla, we predict the potential impacts of spring staging resource utilisation on future breeding success. Although staging is of short duration compared to the other components of annual cycles of migratory species, our results suggest that the quality of staging grounds may be vitally important to population processes.

Sexual competition explains patterns of individual investment in territorial aggression in western bluebird winter groups

In central California, western bluebirds, Sialia mexicana, live year-round on their breeding territories, feeding extensively on mistletoe berries through the winter. In spring, they usually breed as pairs and occasionally have helpers, whereas in winter they live in groups of up to 13 birds including family members and unrelated immigrants. Individuals of both sexes and all ages defend the winter territory against conspecifics. We presented caged male and female decoys to free-living groups of western bluebirds to test predictions of two hypotheses for adaptive variation in individual investment in winter territorial defence: kin value (kin selection) and reproductive competition (future breeding success). We found that individual investment in defence did not increase with kin value (the number of offspring equivalents that an individual had in the group) but varied as predicted by reproductive competition. Females spent more time on cages of female decoys than they did on cages of male decoys, but they did not differ in their frequency of aggressive displays (hops, wing flicks) towards intruders of either sex. In contrast, males spent equivalent periods on the cages of decoys of both sexes, but they hopped more frequently on cages of males. Although the form of aggression differed for males and females, aggression for both tended to be more pronounced towards same-sex conspecifics. The persistent effect of group size as a negative covariate indicates that group living enables individuals to reduce time spent in active territory defence. Members of large groups were able to reduce their investment while maintaining the same level of response to intruders as did members of smaller groups. Patterns of response to caged intruders provide novel support for the hypothesis that sexual competition is important in territorial defence outside the breeding season.

Impact of Forestry Practices on Fitness Correlates and Population Productivity in an Open‐Nesting Bird Species

In the boreal forests of Fennoscandia, over 99% of forest area has been altered by forestry practices, which has created forest with age structures and stand characteristics that differ from primary forest stands. Although many researchers have investigated how forestry affects species abundance, few have assessed how forestry practices affect fitness correlates of species living in altered habitats, and this has negatively affected management efforts. We experimentally addressed the effect of standard forestry practices on fitness correlates of an open-nesting, long-lived bird species typical to boreal forests of Eurasia, the Siberian Jay (Perisoreus infaustus). We used a before-after comparison of reproductive data on the level of territories and found that standard forestry practices had a strong negative effect on the breeding success of jays. Both partial thinning of territories and partial clearcutting of territories reduced future breeding success by a factor of 0.35. Forestry practices reduced territory occupancy. Thus, over the 15 years of the study, productivity of the affected population declined over 50% as a result of territory abandonment and reduced breeding success. Results of previous studies on Siberian Jays suggest that the strong effect of forest thinning on fitness is explained by the fact that most common predators of nests and adults are visually oriented and thus thinning makes prey and nests more visible to predators. The consequences of thinning we observed are likely to apply to a wide range of species that rely on understory to provide visual protection from predators. Thus, our results are important for the development of effective conservation management protocols and for the refinement of thinning practices.

Differential resource allocation strategies in juvenile elephant seals in the highly seasonal Southern Ocean

Environmental conditions experienced in early life affect growth and influence life his- tory strategies, especially in seasonal environments. We studied the seasonal and sexual variation in resource allocation in juvenile southern elephant seals to investigate whether they show a seasonal decline in growth. We also examined whether sexual differences in growth may lead to separate growth strategies that suit each sex in maximizing fitness. We examined the variation in length (as a measure of somatic growth), body mass and condition of 470 individual 1- to 4-yr-old elephant seals relative to their different growth strategies. Applying a novel growth function, we observed increased somatic growth in summer compared to winter. Males were larger, had higher proportions of lean tissue and grew faster than females, demonstrating the evolution of a male growth strategy of attaining maximum size quickly, and a female strategy of achieving primiparity at an early age. This evidence supports the idea that seasonal patterns reflect seasonal variation in prey availability and quality, and differential growth strategies promote optimal resource allocation and increase an indi- vidual's probability of survival and future breeding success in the highly dynamic and seasonal Southern Ocean.

Winter climate affects subsequent breeding success of common eiders

AbstractThe phenology of spring migration depends on the severity of the preceding winter and approaching spring. This severity can be quantified using the North Atlantic Oscillation (NAO) index; positive values indicate mild winters. Although milder winters are correlated with earlier migration in many birds in temperate regions, few studies have addressed how climate‐induced variation in spring arrival relates to breeding success. In northern Europe, the NAO‐index correlates with ice cover and timing of ice break‐up of the Baltic Sea. Ice cover plays an important role for breeding waterfowl, since the timing of ice break‐up constrains both spring arrival and onset of breeding. We studied the effects of the winter‐NAO‐index and timing of ice break‐up on spring migration, laying date, clutch size, female body condition at hatching and fledging success of a short‐distance migrant common eider (Somateria mollissima) population from SW Finland, the Baltic Sea, 1991–2004 (migration data 1979–2004). We also examined the correlation between the NAO‐index and the proportion of juvenile eiders in the Danish hunting bag, which reflects the breeding success on a larger spatial scale. The body condition of breeding females and proportion of juveniles in the hunting bag showed significant positive correlations with the NAO, whereas arrival dates showed positive correlations and clutch size and fledging success showed negative correlations with the timing of ice break‐up. The results suggest that climate, which also affects ice conditions, has an important effect on the fledging success of eiders. Outbreaks of duckling disease epidemics may be the primary mechanism underlying this effect. Eider females are in poorer condition after severe winters and cannot allocate as much resources to breeding, which may impair the immune defense of ducklings. Global climate warming is expected to increase the future breeding success of eiders in our study population.

Diagnosis, surgical treatment, and performance after unilateral castration in breeding bulls: 21 cases (1989-1999).

To evaluate signalment, surgical treatment, postoperative complications, and future breeding success or semen production in a group of bulls with naturally occurring disease of the scrotum or testis. Retrospective study. 21 bulls that underwent unilateral castration after evaluation for scrotal swelling. A computer-assisted search of medical records at 2 veterinary teaching hospitals was performed. Historical, diagnostic, surgical, and follow-up data were collected and analyzed for those bulls with scrotal swelling that underwent unilateral castration. Four of 5 pasture breeding bulls and 9 of 10 semen collection-center bulls successfully bred cows or produced viable semen within 6 months of surgery. Fourteen of 21 surgical procedures were performed after induction of general anesthesia. Sixty-six percent of procedures were performed as open castrations. Seventy-one percent of bulls developed postoperative complications, most of which were mild swellings. Unilateral castration returned 13 of 15 bulls with unilateral disease of the scrotum or testis to productive service by 6 months after surgery. Unilateral castration is an effective treatment for unilateral disease of the,scrotum or testis in bulls, allowing return to reproductive function.

Replacement males in the western bluebird: opportunity for paternity, chick-feeding rules, and fitness consequences of male parental care

In western bluebirds (Sialia mexicana), most pairs remain together for life and share equally in post-hatching parental care. We removed resident males of socially monogamous pairs during laying and after clutch completion to examine chick-feeding rules used by replacement males and current and future fitness consequences of paternal care. Replacement males were not infanticidal and 7 (47%) fed nestlings. Feeding replacement males and the females they joined fed at rates similar to controls. Females without a feeding replacement male compensated by feeding more themselves so that overall feeding rates were not compromised, but they reduced their brooding time. Unlike assisted females, unassisted females exhibited reduced nesting success and their 14-day-old chicks weighed less than controls. Field metabolic rates of unassisted females were 17% higher than those of control females, but the difference was not statistically significant. Older females were better able to raise young without the male's help than were yearling females. Female condition was not affected by male provisioning and unassisted females were as likely to survive to the next breeding season as assisted females. We found no future benefits of provisioning by replacement males; those that fed were no more likely to breed with the female on her subsequent attempt than were males that did not feed, and subsequent clutch sizes were not reduced for females rearing young without the male's help. These experiments suggest that male parental care increases nesting success in western bluebirds and that replacement males use an all-or-none rule to determine whether or not to feed chicks: if they are present during the fertile period they feed at typical rates; if they are not, they usually do not feed at all. Because chick-feeding by males is tied to opportunity for paternity, influences success in the current nest, and does not affect the male's future breeding success, it appears to be parental rather than mating effort.

Prospecting enhances breeding success of first-time breeders in the great cormorant,Phalacrocorax carbo sinensis

In many species of colonial seabirds, young birds visit colonies in the years before they start breeding. This prospecting behaviour may allow them to obtain information that could enhance their future breeding success. We examined the reproductive consequences of prospecting behaviour in the colonial great cormorant, and found support for this idea. New breeders that had been prospecting actively in the previous year obtained breeding sites of higher quality (i.e. closer to sites where conspecifics had fledged young in the previous year) and had higher breeding success than those that had been less active. Prospecting occurred mostly late in the breeding season, and coincided with the time when the majority of the eggs had hatched but before the chicks started fledging, that is, when breeding success in the colony reflected habitat suitability. These results are thus consistent with the use of conspecific reproductive performance as a cue for the quality of a breeding habitat as expected from the ‘performance-based conspecific attraction hypothesis’.

Brood size manipulations within the natural range did not reveal intragenerational cost of reproduction in the Willow TitParus montanus

To test for the existence of a reproductive cost, we manipulated brood sizes (‐2 and +2 nestlings) over 6 years in a northern population of Willow TitsParus montanusbreeding in natural holes. Possible effects were sought in subsequent survival and fecundity of the parents. Parents given extra chicks made more feeding visits than did parents with reduced and control broods. However, this was not reflected in differences in parental body‐weight between groups at the end of the nestling period. Brood size manipulation did not significantly affect female or male survival. In 4 out of 6 years, there was a weak and nonsignificant effect on male survival, consistent with a cost of reproduction. Female and male fecundity in the year following the experiment was not affected by the manipulations. Thus, the data do not give evidence of an intragenerational cost of reproduction in the Willow Tit. Parents appeared unwilling to increase their breeding effort to a level which jeopardized their own survival or future breeding success. It is possible that, because of the time constraints in northern latitudes, females work under their capacity and lay smaller clutches than would otherwise be most profitable. Thus, no costs to the parents would be expected as a consequence of manipulations. These results suggest that the current reproductive rate is not maintained by reproductive cost in the Willow Tit. However, the results do not rule out the possibility that selection has operated outside the current range of reproductive rates during evolutionary history of the species.

Reproduction and growth in bank voles Clethrionomys glareolus: the effect of food‐quality and density manipulations in a laboratory colony

Young laboratory raised bank voles Clethrionomys glareolus, originating from a cyclic population at low phase, were experimentally subjected to manipulations of food and density This was done to assess possible effects of the juvenile environment on later breeding success Juveniles were exposed to the expenmental treatments for 40 d previous to pairingThe study revealed that a high population density in itself can increase future breeding success as compared to low density This effect was only found m females There were also indications that high density led to arrested growth in subordinate females

Spatial Behavior as a Predictor of Infanticidal Individuals in Columbian Ground Squirrels

Home range behavior and spatial relationships of chases were examined for differences that might indicate which sex-age classes of Columbian ground squirrels (Spermophilus columbianus) would likely be infanticidal. Locations of individually marked squirrels were recorded at regular intervals and at the start of chases on 2-3 days per week during the 1971 active season. Location maps were used to measure home range size, home range overlap, distances between individuals, and distances between intruders and adult female home burrows. The probability of an adult female chasing another adult female decreased as the distance of the intruder from the owner's burrow increased, but was not related to the distance between the two adult females. Conversely, the probability of an adult female chasing members of other sex-age classes decreased as the distance between the squirrels increased, but was not related to distance of the intruder to the female's burrow. The latter results were also obtained for chases by adult males of members of all sex-age classes. Overlap between home ranges of adult females was significantly less when infants were in their burrows compared to gestation and post-lactation periods. However, overlap of adult female home ranges by those of other sex-age classes did not change seasonally. These results suggest that only adult females are likely to be infanticidal, which agrees with the two observations so far reported. They do not support Sherman's (1981) prediction that yearling males will also be infanticidal. Among the Marmotini, infanticide has been observed in Marmota flaviventris (Steiner 1972; Armitage et al. 1979; Brody and Melcher 1985), Cynomys ludovicianus (Hoogland 1985), Spermophilus beldingi (Sherman 1981), S. parryii (McLean 1983), S. columbianus (Balfour 1983; Waterman 1984), and S. beecheyi (Trulio et al. 1986). Circumstantial evidence (e.g. cannibalism, aggression) suggests it probably occurs in other members of the ground squirrel genus Spermophilus (Michener 1982; Sherman 1982). It may be a widespread but low frequency behavior among the Marmotini in general. Field documentation is difficult because the actual killing may occur below ground. Infanticide in the Marmotini conforms to two of the five hypotheses for the adaptiveness of infanticide reviewed by Hausfater and Hrdy (1984). Some individuals, most commonly adult females, rarely eat their victims. They may be increasing future reproductive success by reducing competition for burrows or other resources that they, or their own offspring, will need. Other infanticidal individuals, most often males, eat at least part of the dead juveniles. They may be getting protein important for rapid growth, overwintering survival, and future breeding success. Both hypotheses may apply for some individuals. Both of the reported observations of infanticide in Columbian ground squirrels (S. columbianus) involved resident adult females that had litters of their own (Balfour 1983; Waterman 1984). Sherman (1981), however, predicted that males of this species might be infanticidal, as are those of arctic ground squirrels (S. parryii), because the social systems of the two species are similar. Although direct observations of infanticide are mandatory to clearly understand this behavior in ground squirrels, differences in the ways parents interact with other individuals can suggest which individuals in a species pose a threat of infanticide. The