Meeting Abstract

P2.26  Monday, Jan. 5  Intraclutch variation in egg characteristics facilitating hatching synchrony in Canada geese CLARK, Mark*; BOONSTRA, Todd A.; REED, Wendy L.; North Dakota State University; United States Fish and Wildlife Service; North Dakota State University m.e.clark@ndsu.edu

In birds, females may regulate hatching synchrony in offspring by delaying the onset of incubation. However in groups such as waterfowl, incubation begins before the clutch is complete and the offspring hatch simultaneously, indicating that embryonic development varies within the clutch. Mechanisms facilitating the differential development of offspring within clutches of these species have not been identified. We quantified embryonic metabolism, conductance, shell characteristics and rapid yolk development in eggs from complete clutches from a free-living population of Canada geese (Branta canadensis). We found that metabolic rates are inherently higher for embryos from eggs laid later in the clutch, rates of water loss are also higher from eggs laid later in the clutch and shell porosity increases for eggs laid later in the clutch. However, growth of yolk during the rapid yolk phase did not differ among eggs in a clutch. We hypothesize that embryonic development is regulated through the interaction between shell characteristics and vascular development during the earliest stages of incubation in waterfowl and related species.