Sitting ducklings: Timing of hatch, nest departure, and predation risk for dabbling duck broods

Abstract

For ground‐nesting waterfowl, the timing of egg hatch and duckling departure from the nest may be influenced by the risk of predation at the nest and en route to wetlands and constrained by the time required for ducklings to imprint on the hen and be physically able to leave the nest. We determined the timing of hatch, nest departure, and predation on dabbling duck broods using small video cameras placed at the nests of mallard ( Anas platyrhynchos ; n = 26), gadwall ( Mareca strepera ; n = 24), and cinnamon teal ( Anas cyanoptera ; n = 5). Mallard eggs began to hatch throughout the day and night, whereas gadwall eggs generally started to hatch during daylight hours (mean 7.5 hr after dawn). Among all species, duckling departure from the nest occurred during daylight (98%), and 53% of hens typically left the nest with their broods 1–4 hr after dawn. For mallard and gadwall, we identified three strategies for the timing of nest departure: (a) 9% of broods left the nest the same day that eggs began to hatch (6–12 hr later), (b) 81% of broods left the nest the day after eggs began to hatch, and (c) 10% of broods waited 2 days to depart the nest after eggs began to hatch, leaving the nest just after the second dawn (27–42 hr later). Overall, eggs were depredated at 10% of nests with cameras in the 2 days prior to hatch and ducklings were depredated at 15% of nests with cameras before leaving the nest. Our results suggest that broods prefer to depart the nest early in the morning, which may best balance developmental constraints with predation risk both at the nest and en route to wetlands.

Predator Environment Does Not Predict Life History in the Morphologically Constrained Fish Alfaro cultratus (Cyprinodontiformes: Poeciliidae)

“…Predator environments have often been used to study the effects of mortality rate on life history strategies (Law, 1979;Reznick and Endler, 1982;Johnson and Belk, 1999;Gosline and Rodd, 2008) and have been found to affect a wide variety of taxa, including fish, anurans, and insects. Among other things, the presence of a predator can influence timing and size of maturation and changes among developmental stages (Chivers et al, 2001;Johnson, 2001;Hilton et al, 2002;Stoks et al, 2006;Peterson et al, 2019), growth rate (Lardner, 2000;Altwegg, 2002;Šupina et al, 2016;Brown et al, 2018;DeWitt et al, 2019), and investment in offspring (Johnson and Belk, 2001;Gorini-Pacheco et al, 2017). Previous work consistently finds divergent life history patterns in high-predation and lowpredation environments.…”

Wetland Availability and Salinity Concentrations for Breeding Waterfowl in Suisun Marsh, California

“…Breeding hens take incubation breaks to feed and drink in nearby wetland habitat (Figure 2; Casazza et al 2020;Croston et al 2020Croston et al , 2021 and then leave the nest with their ducklings within 2 days of hatch (Peterson et al 2019) and move their brood to nearby wetland habitats (Casazza et al 2020; Figure 2). These wetlands are brackish and highly managed within the marsh, and their salinity concentrations vary extensively, which has important implications for the survival and growth of ducklings (Krista et al 1961;Schmidt-Nielsen and Kim 1964;Swanson et al 1984;Mitcham and Wobeser 1988a,b;Barnes and Nudds 1991;Moorman et al 1991;Stolley and Meteyer 2004;DeVink et al 2005).…”

“…Although dabbling ducks, such as mallard (Anas platyrhynchos) and gadwall (Mareca strepera), typically nest in upland habitat, hens take daily incubation breaks to forage in nearby wetlands and may also assess those wetlands as future brood-rearing sites (Casazza et al 2020;Croston et al 2020;Croston et al 2021). Shortly after hatch, hens move ducklings to nearby wetland habitat suitable for brood rearing (Mauser et al 1994a;Peterson et al 2019). The accessibility and quality of available wetland habitats are important factors that influence duck reproductive success (Mauser et al 1994b).…”

Machine learned daily life history classification using low frequency tracking data and automated modelling pipelines: application to North American waterfowl

“…We annotated daily activity into 8 mutually exclusive life history states (Fig. 2 , Table 1 ) using independent data [ 34 , 35 ] or algorithmic identification of activity [ 24 , 30 ] to develop preliminary classifications which were verified visually by waterfowl biologists using supplemental information on individual fate and longer sequencies of location data. Four classes reflected phenologically-mediated life history states: nesting, brooding, molting, dead.…”