Abstract
Incubation starts during egg laying for many bird species and causes developmental asynchrony within clutches. Faster development of late-laid eggs can help reduce developmental differences and synchronize hatching, which is important for precocial species whose young must leave the nest soon after hatching. In this study, we examined the effect of egg laying sequence on length of the incubation period in Wood Ducks (Aix sponsa). Because incubation temperature strongly influences embryonic development rates, we tested the interactive effects of laying sequence and incubation temperature on the ability of late-laid eggs to accelerate development and synchronize hatching. We also examined the potential cost of faster development on duckling body condition. Fresh eggs were collected and incubated at three biologically relevant temperatures (Low: 34.9°C, Medium: 35.8°C, and High: 37.6°C), and egg laying sequences from 1 to 12 were used. Length of the incubation period declined linearly as laying sequence advanced, but the relationship was strongest at medium temperatures followed by low temperatures and high temperatures. There was little support for including fresh egg mass in models of incubation period. Estimated differences in length of the incubation period between eggs 1 and 12 were 2.7 d, 1.2 d, and 0.7 d at medium, low and high temperatures, respectively. Only at intermediate incubation temperatures did development rates of late-laid eggs increase sufficiently to completely compensate for natural levels of developmental asynchrony that have been reported in Wood Duck clutches at the start of full incubation. Body condition of ducklings was strongly affected by fresh egg mass and incubation temperature but declined only slightly as laying sequence progressed. Our findings show that laying sequence and incubation temperature play important roles in helping to shape embryo development and hatching synchrony in a precocial bird.
Highlights
Incubation is an important stage of reproduction in birds during which parents seek to balance their needs with those of developing embryos
High incubation temperature shortens the incubation period, but accelerated embryonic development can be costly to young birds by increasing oxidative damage [5,6,7]
We examined the effect of egg laying sequence and incubation temperature on length of the incubation period in Wood Ducks
Summary
Incubation is an important stage of reproduction in birds during which parents seek to balance their needs with those of developing embryos. Evidence from a variety of species suggests that maintaining eggs at an optimal temperature between 35.5 ̊C and 38.5 ̊C during incubation is critically important for proper embryo development [1]. Eggs incubated at low temperatures, for example, develop more slowly and produce neonates of reduced quality and fitness [2,3,4]. High incubation temperature shortens the incubation period, but accelerated embryonic development can be costly to young birds by increasing oxidative damage [5,6,7]. Partial incubation produces a size hierarchy within broods that may aid brood reduction during food shortages and improve reproductive success [15], but see [16]
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