Research outline

My  research on grebes at CWE is focusing primarily on two species,Red-necked Grebe (Podiceps grisegena) and Horned Grebe (Podiceps auritus). I am investigating several aspects of the annual cycle in these species, examining life history strategies in grebes.  Life history questions being examined include, pair formation, breeding site and mate fidelity, breeding and parental care, and moult.Photo (left): A Red-necked Grebe chick, aged 6 weeks, ready to be released. Note the bold facial stripes on the grebe. Chicks have unique facial patterns that can be used in the field to indentify individuals during their first 5-8 weeks of life.When and where do grebes form pair bonds?  While most birds find mates at breeding areas, some birds find mates away from breeding areas, such as atwintering sites.  Pair formation in some, such as many waterfowl, may occur months before breeding.  Various hypotheses have been offered to explainthe circumstances in which birds might form early pair bonds.  In examiningthe question in grebes, we can evaluate the generality of some of thesehypotheses.  Additionally, pair formation timing and location has important implications for genetic population structure.  Fieldwork for this questiontakes place both at grebe wintering areas in southern coastal BC, and atbreeding sites near Yellowknife, NT.Patterns of mate and breeding site fidelity in Horned Grebes and Red-neckedGrebes are being examined through banding and colour marking of grebesnesting near Yellowknife, NT.  Habitat characteristics that influencepatterns of site and mate fidelity may also influence timing of pair formation.  Red-necked Grebes show fairly high levels of both mate and sitefidelity at Yellowknife, while Horned Grebes appear more flexible in theiryear-to-year choices of both mates and breeding ponds. 

 Photo (right): A Horned Grebe chick, aged 6 weeks, colour-banded near Yellowknife, NT. Note the impressively large feet and lobed toes, a feature common to all grebes.
How grebes meet the demands of raising young is another question under study.  Of particular interest is how the costs of parental care are balanced between mates and against other demands of the annual cycle, suchas moult.  Grebes pose many interesting questions about reproduction strategies.  They have shared parental care, asynchronous hatching of young (which leads to competitive disparities in the brood), and, in somespecies, brood division between parents in later stages of brood rearing. 

Photo (left):Adult Horned Grebe in breeding plumage, nesting near Yellowknife, NT. Sexes are similar in appearance, but males are generally a bit larger and slightly "fancier" than femaleswhen in high breeding plumage. This is hard to judge in lone birds, but when pairs are viewed together, it is often possible to distinguish them. During banding, bill dimensions and weight are used to help determine sex.

Finally, we are interested in how moult interacts with breeding, migration, and pair formation strategies in grebes.  Red-necked and Horned Grebes undergo one complete moult in late summer/fall and a partial moult in latewinter/spring.  The complete moult includes simultaneous molt of flight feathers, rendering the grebes flightless for about 3 weeks or more.Habitat choices for the simultaneous wing moult are of particular interestboth to understand life history strategies in grebes, and for conservationpurposes.  A few moult sites have been identified for Red-necked and HornedGrebes, but much of their North American  populations are unaccounted forduring this period. Photo (right):Adult Horned Grebe in breeding plumage, nesting near Yellowknife, NT. Horned grebes often begin body moult by mid-June, so their impressive head plumes do not last long.
 

More on Grebe research by CWE