Waterfowl Food Sources for Egg Production

Lesser Scaup 3 713

Learning about the food sources of waterfowl that inhabit the refuge allow us to better manage those resources to ensure a healthy population.  This study investigates the source of food used in producing eggs using the Lesser Scaup.


Simple Title of Study: What food sources do Lesser Scaup use in producing their clutches

Authors:

Kyle A. Cutting, Keith A. Hobson, Jay J. Rotella, Jeffrey M. Warren, John Y. Takekawa, Susan E.W. De La Cruz and Michael Parker. (eggs)?

Short Description of Science Project:

This project was designed to find out if water fowl, more specifically, the Lesser Scaup, a common duck that breeds in our refuge, use food found on the refuge or from fat reserves stored prior to arrival on the refuge. It has been known that some shore birds and songbirds get all their nutrients for egg laying at their breeding sites, while some larger birds, like the emperor goose rely heavily on stored fat to produce their eggs once they arrive at the breeding site. This study was designed to find out where the Lesser Scaup fits into this continuum of choices of nutrient sources.

How Was It Done?

Lesser Scaup were captured, banded and small pieces of fat (lipids) were extracted surgically before releasing the duck back into the wild. For nests found, one egg was removed and hard-boiled for use in analysis. (76 eggs were used over a four year study period.) This fat was analysed using carbon isotope analysis to attempt to discover the nutrients stored in the fat and the eggs.

Results of the Science Project:

Over the four year study, the average percentage of egg nutrients in Lesser Scaup determined to be from local wetland plant seeds was roughly equal to that from stored fats in the duck, which were presumably stored during the spring migration (while they were away from the refuge.) The dependence on seeds as a local source of fats for producing eggs was an unexpected result of the study. Scaup are commonly though of as preferring amphipods during the breeding season (Amphipods are a small crustacean that looks like a miniature shrimp.) Annual variations in the use of seeds by the ducks was related to the water levels on the refuge which probably affected how easy it was for them to find certain vegetation and seeds in the open water habitats that they prefer prior to breeding and while nesting. The relative amount of local food sources used by the female scaup to produce their eggs was also interesting. The proportion of local food used by the ducks during this study was greater than found in previous studies and points to the importance of providing productive wetlands for nesting female scaup to ensure they find the resources that they need for their egg formation.

By understanding the foraging habits of scaup during the period prior to breeding perhaps wetland managers can focus on providing suitable habitats that ensure a diversity of invertebrate and seed food sources during the time they breed on the refuge and over the ideal places at the refuge.

Duration of Study:

This study was conducted at the Red Rock Lakes National Wildlife Refuge between 2006 and 2009. 

Original Paper:

Title: Relative contribution of lipid sources to eggs of lesser scaup

Published: 2014 by  

Journal of Avian Biology © 2014 Nordic Society Oikos

Link to original paper:PDF

Links to Related papers: To be supplied: Lesser Scaup Breeding Areas: Preferred habitat or Social Interaction?