Influence of incubation recess patterns on incubation period and hatchling traits in wood ducks Aix sponsa

Parental effects are influential sources of phenotypic variation in offspring. Incubation temperature in birds, which is largely driven by parental behavior and physiology, affects a suite of phenotypic traits in offspring including growth, immune function, stress endocrinology, and sex ratios. The importance of average incubation temperature on offspring phenotype has recently been described in birds, but parental incubation behaviors like the duration and frequency of recesses from the nest can be variable. There are few studies describing how or if thermal variation as a result of variable incubation affects offspring phenotype. We incubated wood duck Aix sponsa eggs under three different incubation regimes, based on patterns that occur in nature, which varied in off‐bout duration and/or temperature. We measured incubation period, morphometrics at hatching, and monitored growth and body condition for nine days post hatch. When average incubation temperature was allowed to drop from 35.9°C to 35.5°C as a result of doubled off‐bout duration, we found a significant 2 d extension in incubation period, but no effects on duckling hatch mass, or growth and body condition up to nine days post hatch. However, when average incubation temperatures were equivalent (35.9°C), doubling the duration of the simulated off‐bouts did not influence incubation period or any post hatch parameters. Our results suggest that if incubating parents can maintain favorable thermal environments in the nest via altered behavior (e.g. manipulating nest insulation) and/or physiology (e.g. heat production), parents may be able to avoid the costs of longer incubation periods resulting from increased off‐bout duration.     

Biparental incubation and allofeeding at nests of Sagebrush Brewer's Sparrows

Facultative male incubation and allofeeding are thought to be behavioral adaptations by which male songbirds maximize their fitness by reducing the energetic stress of their mates. However, few data are available for most species that exhibit these behaviors so the extent to which they might enhance male fitness remains unclear. Among North American sparrows, male incubation is known in four species, but the relative contributions of each sex have been estimated for only one species. We quantified biparental incubation and allofeeding in Sagebrush Brewer's Sparrows (Spizella breweri breweri) with 24‐h video surveillance of nests (N = 24) at two locations in northern Nevada. We detected biparental incubation at both sites (17 of 24 nests, 71%), and found that mean constancy (i.e., proportion of 24‐h period eggs were covered) was significantly higher at biparental nests than at uniparental nests, and mean recess duration (i.e., when eggs were uncovered) was significantly shorter. Incubation constancy at biparental nests in our study was the highest yet reported in the genus Spizella (range = 0.87–0.96), and constancy at uniparental nests (mean = 0.76, range = 0.71–0.81) was greater than that of congeners where female‐only incubation is thought to be the norm. Biparental incubation was more likely on colder days, but a comparison of models where incubation strategy and its interaction with ambient temperature were included as independent variables revealed that temperature was not the best predictor of constancy. Allofeeding occurred at very low frequency and only at biparental nests (11 of 20, 55%). Biparental nests with allofeeding had more incubation sessions per hour than biparental nests without allofeeding. The recipient usually left the nest immediately after being fed, and the feeding individual assumed the role of incubator. Our results suggest that some factor other than low ambient temperatures favors biparental incubation by Sagebrush Brewer's Sparrows. One possibility is that male incubation and the resulting increase in incubation constancy may better conceal nests and reduce the likelihood of nest predation. The low frequency of allofeeding at nests with biparental incubation in our study suggests that it serves some function other than improving female nutritional status or reducing activity levels at nests. Rather, allofeeding may serve as an intraspecific signal important for maintaining the social bond between mates.     

Local variation in weather conditions influences incubation behavior and temperature in a passerine bird

Incubation is an important component of avian parental care and slight changes in incubation temperature can affect offspring phenotype. Although many extrinsic and intrinsic factors may generate variation in incubation temperature, they remain underexplored under natural conditions. Using a robust data set encompassing 55 nests, 22 816 behavioral observations, and > 1 million paired ambient and egg temperatures, we describe the relationships among abiotic factors, female incubation behavior, incubation temperature, and incubation period for tree swallows Tachycineta bicolor. We report a large amount of individual variation in incubation behaviors and average incubation temperatures for our study population. The average on‐bout incubation temperature was 34.1°C, with daily egg temperatures ranging from 18.0–39.2°C. Females modulated the number of times they left the nest and the amount of time they stayed off the nest according to interactions between precipitation and temperature patterns. Models generated from our observations predicted that the number of female off‐bouts was the lowest under warm and dry conditions while more off‐bouts were taken under cold and dry or warm and wet conditions. During cold and dry conditions, females stayed off their nest ～4 times longer than under warm and dry conditions. However, this pattern was reversed under periods of rainfall; females tended to take shorter off‐bouts when it was rainy and cold compared to longer off‐bouts during warmer rain events. Furthermore, variation in female behavior was associated with differences in overall incubation temperature such that females that maintained greater incubation constancy produced higher incubation temperatures at a given ambient temperature than those that displayed lower incubation constancy. Our results provide perspective on the timing of breeding, as some of the advantages of breeding early may be countered by cooler, early season temperatures and precipitation that cause reproducing females to favor self‐maintenance at a potential cost to optimal incubation temperatures for offspring development.     

BREEDING BIOLOGY OF THE BEARDED VULTURE IN SOUTHERN AFRICA,PART I: THE PRELAYING AND INCUBATION PERIODS

Brown, C. J. 1990. Breeding biolo of the Bearded Vulture in southern Africa, Part I: The pre-laying and incubation periods. Ostrich 61: 24–32.

In southern Africa the Bearded Vulture Gpaetus barbatus lays its eggs in mid-winter. between the second half of May and the first week of July. Pairs became more active in their nesting areas about six weeks before laying and usually roosted there at night. Courtship flights were less frequent and demonstrative than in Eurasian birds and took place mainly in the late afternoons. During the pre-laying period most nest visits (77%) were to bring nesting material, 92% by the male. All nesting material was arranged by the female. Copulation was always preceded by allopreening, and occurred most frequently in the mornings. No copulation or courtship display took place after the first egg had been laid. Of 18 clutches, 16 (89%) contained two eggs and the remainder one egg. The laying interval was usually 3–5 days (range 2–9 days). Incubation started with the first egg and was evenly shared by both parents during the day, but only the female incubated at night, individual pairs maintained distinctive nest attendance and foraging period timetables, which allowed sufficient time for self-foraging by both parentes. No food was brought into the nest during the pre-laying and incubation periods, but in some pairs food was cached in nearby potholes in cliffs. The incubation period was 56–57 days.     

Partial incubation during egg laying reduces eggshell microbial loads in a temperate‐breeding passerine

Incubation prior to clutch completion may be adaptive if it maintains egg viability by inhibiting eggshell microbial growth, thus reducing the likelihood that the embryo becomes infected. To test this hypothesis, we examined the effect of partial incubation during egg laying on eggshell microbial loads in eastern bluebirds Sialia sialis breeding at a temperate‐zone site. We sampled eggshell microbes prior to and following four days of exposure to either partial incubation during the laying period or ambient environmental conditions without incubation (experimental eggs). Microbial colony counts declined significantly for eggs left in the nest during the laying period but did not vary significantly for eggs exposed to ambient conditions. Initial microbial loads were more similar to those previously reported from tropical than temperate environments, and microbes from potentially pathogenic groups were detected on 88% of first‐laid eggs on the day of laying. Egg viability was maintained when eggs were held indoors for four days without incubation but declined sharply thereafter. Our results suggest that partial incubation during egg laying may enhance egg viability in eastern bluebirds by reducing eggshell microbial loads; these effects appear stronger than those usually reported from the temperate zone.     

Handicapped females receive more feedings during incubation from their mates: support for the female nutrition hypothesis

The female nutrition hypothesis posits that provisioning intensity of incubating females by their mates may depend on female needs and ensure proper incubation and a corresponding high hatching and breeding success of breeding pairs. Here, we have handicapped female pied flycatchers Ficedula hypoleuca at the beginning of incubation by clipping two primaries on each wing and filmed nests during incubation and later nestling provisioning to estimate male involvement in incubation feeding at the nest and in offspring care. Incubation feeding was more frequent at late nests. Correcting for this seasonal effect, incubation feeding was significantly affected by treatment and twice as high at experimental as at control nests. There was no effect of the experiment on female incubation attendance. The handicap did not result in any effect on hatching and breeding success, nestling growth and male or female provisioning and mass at the end of the nestling period. Males adjust their incubation feeding activity at the nest to female energetic requirements during incubation.     

Buildings promote higher incubation temperatures and reduce nest attentiveness in a Neotropical thrush

Incubation is an energetically costly parental task of breeding birds. Incubating parents respond to environmental variation and nest‐site features to adjust the balance between the time spent incubating (i.e. nest attentiveness) and foraging to supply their own needs. Non‐natural nesting substrates such as human buildings impose new environmental contexts that may affect time allocation of incubating birds but this topic remains little studied. Here, we tested whether nesting substrate type (buildings vs. trees) affects the temperature inside the incubation chamber (hereafter ‘nest temperature’) in the Pale‐breasted Thrush Turdus leucomelas, either during ‘day’ (with incubation recesses) or ‘night’ periods (representing uninterrupted female presence at the nest). We also tested whether nesting substrate type affects the incubation time budget using air temperature and the day of the incubation cycle as covariates. Nest temperature, when controlled for microhabitat temperature, was higher at night and in nests in buildings but did not differ between daytime and night for nests in buildings, indicating that buildings partially compensate for incubation recesses by females with regard to nest temperature stability. Females from nests placed in buildings exhibited lower nest attentiveness (the overall percentage of time spent incubating) and had longer bouts off the nest. Higher air temperatures were significantly correlated with shorter bouts on the nest and longer bouts off the nest, but without affecting nest attentiveness. We suggest that the longer bouts off the nest taken by females of nests in buildings is a consequence of higher nest temperatures promoted by man‐made structures around these nests. Use of buildings as nesting substrate may therefore increase parental fitness due to a relaxed incubation budget, and potentially drive the evolution of incubation behaviour in certain urban bird populations.     

Comparison of the egg flotation and egg candling techniques for estimating incubation day of Canada Goose nests

ABSTRACT Both egg flotation and egg candling have been used to estimate incubation day (often termed nest age) in nesting birds, but little is known about the relative accuracy of these two techniques. We used both egg flotation and egg candling to estimate incubation day for Canada Geese (Branta canadensis interior) nesting near Cape Churchill, Manitoba, from 2000 to 2007. We modeled variation in the difference between estimates of incubation day using each technique as a function of true incubation day, as well as, variation in error rates with each technique as a function of the true incubation day. We also evaluated the effect of error in the estimated incubation day on estimates of daily survival rate (DSR) and nest success using simulations. The mean difference between concurrent estimates of incubation day based on egg flotation minus egg candling at the same nest was 0.85 ± 0.06 (SE) days. The positive difference in favor of egg flotation and the magnitude of the difference in estimates of incubation day did not vary as a function of true incubation day. Overall, both egg flotation and egg candling overestimated incubation day early in incubation and underestimated incubation day later in incubation. The average difference between true hatch date and estimated hatch date did not differ from zero ( days) for egg flotation, but egg candling overestimated true hatch date by about 1 d (true – estimated; days). Our simulations suggested that error associated with estimating the incubation day of nests and subsequently exposure days using either egg candling or egg flotation would have minimal effects on estimates of DSR and nest success. Although egg flotation was slightly less biased, both methods provided comparable and accurate estimates of incubation day and subsequent estimates of hatch date and nest success throughout the entire incubation period.     

BREEDING BIOLOGY AND BEHAVIOUR OF THE QUAIL FINCH ORTYGOSPIZA ATRICOLUS

Summary

Nuttall, R.J. 1992. Breeding biology and behaviour of the Quail Finch Ortygospiza atricollis. Ostrich 63:110-117.

During a study of the breeding biology of the Quail Finch Ortygospiza atricollis, observations of nest-building, egg-laying, incubation and nestling periods, and nestling development in a grassland near Pietermaritzburg, South Africa were supplemented with observations of breeding behaviour in captivity. Mean clutch size was 4,5 and eggs were laid at intervals of approximately one day. Incubation began after the third or fourth egg was laid. An incubation period of 15–16 days and an estimated nestling period of 18–19 days was recorded. Incubation and brooding are shared by both sexes. Breeding success was low (26,7% ?28,6%), with most losses resulting from predation during either the egg-laying or incubation stages.     

Prolactin and parental behavior in Adélie penguins: effects of absence from nest, incubation length, and nest failure

Adélie penguin (Pygoscelis adeliae) males and females, nesting in Antarctica, alternate attendance at the nest with absences of many days to forage at sea. We investigated the importance of tactile input from egg and chicks on prolactin levels by observing nest attendance patterns and obtaining blood samples (1) during the first nest exchange of the incubation stage, (2) from birds whose incubation period was artificially increased or decreased by about 10 days, and (3) from birds whose nests had failed. Prolactin levels in females after 8 to 11 days of absence from the breeding colony did not differ from those in incubating males and did not change after females resumed incubation. Moving eggs between nests resulted in nests in which chicks hatched after about 26, 36 (normal), or 46 days. Duration of incubation did not affect prolactin levels in the parents measured during incubation, at the pip stage, hatch stage, or early brood stage. Adults first left their chicks unguarded on about the same calendar date, regardless of chick age. However, chicks from long incubation nests averaged 8 days younger when they were left unguarded than chicks from control or short-incubation nests. In females, there was no effect of nest failure on prolactin levels. In males, prolactin levels were slightly lower after nest failure than in males tending nests. Testosterone was significantly higher in males after nest failure than in males still tending nests. Prolactin is elevated in Adélie penguins as part of the program of cyclical hormonal changes that accompany the lengthy reproductive season and is relatively independent of tactile input. Sustained prolactin secretion is probably required for the maintenance of parental behavior in offshore feeding species that must be absent from the nest for many days at a time.     

Behaviour of the yellow-eyed penguin chick

The ontogeny of yellow-eyed penguin ( Megadyptes antipodes ) chick behaviour follows the order of development determined by Nice (1962) for several species of birds, and by Spurr (1975) for the Adélie penguin ( Pygoscelis adeliae ). Feeding and comfort behaviours are the first to develop, followed by locomotion and aggressive behaviour.
Active solicitation of food may occur at one day of age. Chicks initially use non-visual cues to mediate begging. After their eyes open on the third or fourth day there is an increase in the use of visual stimuli, and begging occurs most often following adult nest relief. Sibling rivalry is not intense, occurring least during feeding, and in general both chicks are fed at each session.
The chicks are brooded for the first 21–25 days. At sparsely vegetated nest sites overheating may occur after 21 days and down-covered chicks will seek shade and pant in hot weather.
Throughout the 6–7 weeks of the guard phase there is a decrease in the amount of time spent resting in a prone posture, and an increase in exploratory, locomotory behaviour. During the post-guard phase, and until fledging and independence at 15 weeks after hatching, chicks may wander up to 20 m from the nest bowl during exploration, shade-seeking and feeding.
Adults feed only their own chicks, and chicks appear to beg only from their parents. Dense vegetation and long distances between nests tend to restrict contact between adults and chicks from neighbouring nests, and prevent the formation of large chick crèches.     

The Early Development of Pygoscelis adeliae (Adélie Penguin) up to the Formation of the Neural Tube

The early embryonic development of Pygoscelis adeliae, up to the stage with fused neutral folds, was investigated by means of serial sections and compared with the development of the chick (Gallus domesticus). The total incubation time in the penguin is about 35 days, compared with about 20 days in the chick (Herbert 1967). This superior rate of development in the chick is likewise recognized in the early period of development; for fusion of neural folds is achieved 45–49 hours after laying in the chick and 6–7 1/2 days incubation in the penguin. Furthermore the time of origin and shape of the neural tube, notochord and heart show recognizable differences in the two genera.     

THE BREEDING BIOLOGY OF THE BLACK-BELLIED STORM-PETREL FREGETTA TROPICA

The breeding cycie and habits of the Black-bellied Storm-petrel are described from observations made over three seasons at Signy Island, South Orkney Islands. The species is strictly nocturnal on land and nests in stable scree slopes. With an estimated population of 100–200 pairs, Fregetta tropica is the rarest petrel breeding on the island. In general, the breeding cycle of F. tropica resembles that of Oceanites oceanicus. Birds usually arrive from mid-November onward and return to the same nest and mate in successive seasons. The female is absent from the nest for a week or more before the egg is laid, during which time the male continues to visit the site. From ten laying dates, egg laying appears normally to begin during the last week in December, but evidence is given that, in 1966-67, laying was delayed by heavy winter snow build-up coupled with a late melt. The egg comprises 26 % of the body weight of the female. Incubation is by both sexes in alternate spells of three days, the whole period lasting 38–44 days. The chick is left alone in the nest by the parents almost immediately after hatching. Chick growth is described briefly and the effects of drift snow on development are discussed. The fledging periods of two chicks were 65 and 71 days, departure from the nest taking place in mid-April. Measurements of 36 Signy Island birds show considerable variability but are similar to those from other breeding localities.     

Hormonal correlates of parental behavior in yellow-eyed penguins (Megadyptes antipodes)

Penguins show varying degrees of brood reduction behavior, from obligate brood reducers to brood maximizers, and we hypothesize that this is associated with differences in prolactin secretion. To address this hypothesis, we determined the breeding season prolactin profile of the yellow-eyed penguin (Megadyptes antipodes) for comparison with those of other penguin species found in the literature. We also measured sex steroid plasma concentrations to better characterize the reproductive cycle of the species. Plasma concentrations of prolactin increased from early in the season, reaching a peak during late incubation, and remained elevated up to the guard period. This general pattern was similar to that of other penguins for which we have corresponding data. However, we found that throughout the laying period, prolactin titers in yellow-eyed penguins remained elevated while they fell to basal levels after the laying of the first egg in macaroni penguins, which corresponds to differences in incubation behavior during this time. We conclude, therefore, that differences in the brood reduction behavior in penguins, may be reflected in the pattern of PRL concentrations around the time of egg laying.     

Isolation and characterization of microsatellite loci from the yellow-eyed penguin (Megadyptes antipodes)

Twelve microsatellite loci were isolated and characterized in the endangered yellow-eyed penguin (Megadyptes antipodes) using enriched genomic libraries. Polymorphic loci revealed two to eight alleles per locus and observed heterozygosity ranged from 0.21 to 0.77. These loci will be suitable for assessing current and historical patterns of genetic variability in yellow-eyed penguins.     

The effects of heterospecifics and climatic conditions on incubation behavior within a mixed‐species colony

Parental incubation behavior largely influences nest survival, a critical demographic process in avian population dynamics, and behaviors vary across species with different life history breeding strategies. Although research has identified nest survival advantages of mixing colonies, behavioral mechanisms that might explain these effects is largely lacking. We examined parental incubation behavior using video‐monitoring techniques on Alcatraz Island, California, of black‐crowned night‐heron Nycticorax nycticorax (hereinafter, night‐heron) in a mixed‐species colony with California gulls Larus californicus and western gulls L. occidentalis. We first quantified general nesting behaviors (i.e. incubation constancy, and nest attendance), and a suite of specific nesting behaviors (i.e. inactivity, vigilance, preening, and nest maintenance) with respect to six different daily time periods. We employed linear mixed effects models to investigate environmental and temporal factors as sources of variation in incubation constancy and nest attendance using 211 nest days across three nesting seasons (2010–2012). We found incubation constancy (percent of time on the eggs) and nest attendance (percent of time at the nest) were lower for nests that were located < 3 m from one or more gull nest, which indirectly supports the predator protection hypothesis, whereby heterospecifics provide protection allowing more time for foraging and other self‐maintenance activities. To our knowledge, this is the first empirical evidence of the influence of one nesting species on the incubation behavior of another. We also identified distinct differences between incubation constancy and nest attentiveness, indicating that these biparental incubating species do not share similar energetic constraints as those that are observed for uniparental species. Additionally, we found that variation in incubation behavior was a function of temperature and precipitation, where the strength of these effects was dependent on the time of day. Overall, these findings strengthen our understanding of incubation behavior and nest ecology of a colonial‐nesting species.     

Cooperative incubation behaviour in a super dense Common Eider Somateria mollissima colony

Capsule Common Eiders at Rif in west Iceland commonly show joint nest attendance, which may be an exaggerated behavioural response to the visual stimulus of many nests so close to their own nest. This represents a new insight into incubation behaviour in colonies with extremely high nest densities.     

The breeding biology of the Scimitarbilled Woodhoopoe

Steyn, P. 1999. The breeding biology of the Scimitarbilled Woodhoopoe. Ostrich 70 (3&4): 173–178.

The breeding biology of the Scimitarbilled Woodhoopoe Rhinopomastus cyanomelas was studied at two sites in Zimbabwe over a 13-year period from 1964–1977. The pairs were resident, remained together throughout the year, and inspected their nest sites occasionally during the non-breeding season. The breeding season extended from August to December with a marked September/October peak. Eggs were laid at daily intervals. Clutch size averaged 2.9 (range 2–4). Incubation began either with the penultimate or last laid egg. During the 13–14 day incubation period the female left the nest only occasionally each day and was reliant on the male for food. This pattern continued for four days after the chicks hatch. Thereafter she started to forage and gradually increased her contribution to chick provisioning until she overtook that of the male. With one exception, he never fed the chicks directly and delivered the food to the female. The nestlings were brooded overnight for the first two weeks. The anti-predator response of the young included a malodorous brown exudation from the preen gland and unpleasant liquid excreta. The nestling period was 21–24 days and the young left the vicinity of the nest with their parents and did not return to roost in it. Twelve breeding cycles were monitored and 76% of eggs laid (n=37) produced fledged young. Second broods were raised in the same nest on two occasions after successful rearing of the first, presumably by the same pair, but the birds were not individually marked. There was no evidence of helpers at the nest.     

Free‐moving artificial eggs containing temperature loggers reveal remarkable within‐clutch variance in incubation temperature

Incubation is a crucial aspect of avian parental care and measuring incubation temperature in the wild can improve our understanding of life history tradeoffs and inform conservation efforts. However, there are challenges associated with measuring the temperature of eggs in natural nests. Most studies to date have measured incubation temperature by using a single, stationary logger in each nest. However, real eggs are rotated and moved throughout the nest by the parent during the incubation period, and thus, a stationary logger may not accurately represent the temperature experienced by individual eggs within the entire clutch. We recorded incubation temperature in nests by using multiple, mobile artificial egg temperature loggers. We installed six mobile loggers and one stationary logger in wood duck Aix sponsa nests to compare the two logger types in the field. We found that at a given ambient temperature, mobile loggers recorded lower average and more variable temperatures than stationary loggers. Further, temperatures recorded by stationary loggers showed no relationship with clutch size, while mobile loggers captured temperatures that were lower and more variable as clutch size increased. Also, the multiple mobile loggers revealed that eggs within a nest experienced a substantial range of temperatures throughout the incubation period. We discuss potential limitations of this method, but believe that it is a promising way to collect biologically‐relevant incubation temperature data and provides an opportunity to advance our understanding of incubation temperature as a parental effect.