Number Of Eggs In Nest Research Articles

Consequences of a changing environment on the breeding phenology and reproductive success components in a long‐distance migratory bird

AbstractMigratory birds have a narrow time window to breed, especially in the Arctic, where early nesting typically yields the highest reproductive success. We assessed temporal changes (1991–2015) in reproductive success components in relation to timing of breeding in greater snow geese (Chen caerulescens atlantica). This species breeds in the Canadian Arctic, a region that has experienced a strong warming trend. We tested the effect of laying or hatching date, year and their interaction on six reproductive components: Total clutch laid, nesting success, egg survival, hatching success, prefledging, and postfledging survival. Over 25 years, mean laying date changed little, even though it advanced 1.8 days in early breeders and was delayed 3 days in late breeders. Likewise, the number of eggs in nests initiated early in the season decreased by 0.6 egg, whereas in late nests it increased by 0.3 egg. Success of nests initiated early and late in the season was lower than nests initiated near the population mean, and consistently increased over time. The proportion of eggs surviving to partial predation and postfledging survival decreased with laying date but the pattern did not change over time. In contrast, prefledging survival was not affected by laying date initially but declined in nests initiated late in the season toward the end of the study. Overall, nests initiated close to the population mean showed little temporal change for most components of reproductive success and seem to be less affected by environmental change than nests initiated early and late in the season.

Asynchronous reproduction in three species of crocodilians in south-eastern Amazonia

ABSTRACTWe studied reproduction of three species of crocodilians, Paleosuchus trigonatus, Caiman crocodilus and Melanosuchus niger, in the Xingu River, near the Belo Monte hydroelectric dam. The periods of laying and hatching of eggs were estimated for each nest before (2013–2014) and after (2016–2017) the river was dammed and the reservoir was formed. Nesting of the three species occurred between August and December, but was largely asynchronous; nest construction peaked in September for P. trigonatus, October for M. niger and November for C. crocodilus. Reservoir filling had little effect on the laying period of any of the species. Nests of P. trigonatus and M. niger were always within 0–12 m of the bank, whereas nests of C. crocodilus, which nests later in the season when flooding is more likely, were up to 100 m from the nearest water body. There was no relationship between distance from water and the number of eggs in nests, suggesting that larger and presumably more experienced females do not lay at different distances from the bank in any of the species.

Do wood ducks use the quantity of eggs in a nest as a cue to the nest’s value?

Breeding birds use a variety of cues to choose a nest site. For conspecific brood parasites, the number of eggs in a nest may be an important indicator of nest stage (laying or incubating) and the resulting prospective value of the nest. In precocial birds, such as wood ducks (Aix sponsa), a parasitic female should lay her eggs during the host's laying stage to ensure hatch synchrony with the host. Incubation and hatching success may also be compromised in large clutches. Accordingly, parasitic females should respond to the number of eggs already present in a potential hosts' nest and should preferentially lay eggs in nests with smaller clutches. We conducted a field experiment using simulated nests containing different numbers of host eggs to test this hypothesis. When offered a choice of nests containing clutches of 5, 10, 15, or 20 eggs, females were significantly more likely to lay eggs in the 5- and 10-egg treatments, laid more eggs in total in the smaller clutch treatments, and were more likely to incubate the nests in the 5- and 10-egg treatments. These results indicate that wood ducks are responsive to quantitative cues, such as the number of eggs in a nest, although we do not yet know if they are able to do so directly by numerical discrimination (i.e., counting). Copyright 2010, Oxford University Press.

セイタカシギの一腹卵数

The number of eggs in nests of the Black-winged Stilt Himantopus himantopus himantopus in areas in Tokyo Metropolis and Chiba Prefecture, around the Tokyo Bay was investigated. The mean ± SE number of eggs in nests was 3.50±0.06 (n=384, range 1-10). Instances of five or more eggs in a nest were suggested to have been produced by two or three females. The mean ± SE of clutch size by monogamous pairs was 3.36±0.05 (n=362, range 1-4).

Egg Production of Cockatiels (Nymphicus hollandicus) Is Influenced by Number of Eggs in Nest after Incubation Begins

Cockatiel eggs hatch asynchronously because most eggs are laid after continuous incubation begins. We manipulated numbers of eggs in the nest after cockatiels began incubating to determine whether number of eggs in the nest influenced clutch size. We also measured plasma prolactin 2, 7, 12, and 17 days after egg laying began to determine whether clutch size covaried with prolactin concentration. We found that total egg production was stimulated in pairs for which the rate of egg accrual was reduced by egg removal, while total egg production was inhibited in pairs for which the egg accrual rate was increased by egg addition. Female, but not male, plasma prolactin concentrations correlated negatively with egg production on day of lay 17 but not before. We conclude that egg production in incubating cockatiels is influenced by feedback from the number of eggs in the nest and that clutch termination may be signaled by rising prolactin levels in females.

Brood Size, Male Fanning Effort and the Energetics of a Nonshareable Parental Investment in Bluegill Sunfish, Lepomis macrochirus (Teleostei: Centrarchidae)

AbstractWe present a model and an experimental test for a nonshareable parental‐investment behavior (fanning of eggs) using parental male bluegill sunfish. The model predicts that as brood size increases, nonshareable investment into the brood should increase if a parent is to maximize its remaining lifetime reproductive success. The experimental test manipulated the number of eggs in nests and quantified the frequency and tempo of fanning in the field using underwater video equipment. As predicted, male bluegill fanned larger broods more frequently than smaller broods. The fanning tempo (beats per min) did not change with changes in brood size. Parental males lost substantial amounts of body weight during the period of parental care, and lipid extractions revealed a loss in nonpolar lipids. The difference in fanning frequency between large and small broods did not result in differential weight loss for the parents, but parents that fanned more tended to lose more nonpolar lipids from the body tissue than males that fanned less.

On the evolution of nest raiding and male defensive behaviour in sticklebacks (Pisces: Gasterosteidae)

We develop a model to explain the evolution of nest raiding by female sticklebacks based on enhanced female reproductive success derived by creating mating opportunities with the male whose nest has been destroyed. Our model depends critically on the shape of the function relating percentage hatch success to the number of eggs in a male's nest, and the probability that the female will later mate with the male whose nest was raided. Raiding by females will be favoured when the number of eggs in the nest is high providing high egg numbers reduces the percentage hatch rate. High probabilities of mating with the male in question also favour raiding. A second model suggests that males cannot reduce the probability of being raided by limiting the number of eggs in the nest. Instead selection should favour their increasing the number of eggs in the nest. Tests of these models are suggested and their relation to other factors which may influence the evolution of cannibalism are discussed.

Water-Vapor Conductance of Black-Billed Magpie (Pica pica) Eggs Collected along an Altitudinal Gradient

Water-vapor conductance was determined for 78 eggs of Black-billed Magpies (Pica pica) collected along an altitudinal gradient in north-central Colorado and south-eastern Wyoming (range 1,486-2,896 m). Conductance of magpie eggs to water vapor is a function of the number of eggs in nests at the time of collection, indicating that conductance may be related to the order in which an egg is laid. A statistical relationship between altitude and conductance of eggs in our samples probably is spurious, and we conclude that water-vapor conductance of eggs does not vary altitudinally within the geographic area encompassed by our study. The altitudinal decline in water-vapor conductance that has been reported for eggs of several other species of birds seems not to characterize eggs of magpies.

Ovarian Egg Complements and Nests of the Two-Lined Salamander, Eurycea b. bislineata X cirrigera, From Southeastern Virginia

Recent study of the large ovarian egg complement of Eurycea bislineata rivicola Mittleman, by Wood and Duellman (1951:181), showed that gravid females may contain as many as 92 eggs ready for laying prior to the beginning of the nesting season. The maximum number reported in a nest deposited by one female, 50 eggs (H. H. Wilder 1899:235), is far short of the maximum number of larve ova present in some gravid females. Although Wilder (ibid) was referring to the eastern subspecies, E. b. bislineata (Green), this difference raises the question of the relationship reported to exist between number of ovarian eggs and the number of eggs in nests. I. W. Wilder (1924:77) observed that the number of eggs in nests of bislineata is consistent with the numbers of large ova in gravid females from the same region. Reported here are the numbers of large ova in 41 gravid females, and the number of eggs in 29 nests of the two-lined salamander, Eurycea b. bislineata X cirrigera. Females and nests were collected from the same regions on the Virginia coastal plain, principally in the vicinities of Yorktown and Williamsburg. The females were collected from springs and seepages during the winter months (largely January and February) in 1949, 1950, and 1951. These specimens were promptly preserved, and the ovaries were dissected out after hardening. The ovaries contained large yellowish yolk-filled ova, (1.5 to 2.5 mm in diameter) and small white translucent ova (0.3 to 0.75 mm in diameter). Intermediates between these two size-groups of ova were not noted, and only large ova were counted. The 41 females contained a total of 2,931 large ova, with complements ranging from 29 to 115, mean 71.5 ? 20.8 Snoutvent measurements were based on the straight-line distance from the anterior tip of the snout to the inner posterior margin of the cloaca. The females ranged in snout-vent length from 36 to 50 mm, mean 43 ? 3.4. Length measurements were plotted against counts of ova (fig. 1). The correlation between snout-vent length and the number of large ova was evaluated by the product-moment method. It was found that r = 0.695, t = 6.23, indicating that there is considerably less probability than one chance in several hundred that these data do not demonstrate a significant correlation. The number of large ova is related to the length of the female; generally, longer females contain more ova.