When I began work at Trent in 1986 I decided to initiate a long-term study on an arctic-nesting shorebird species. Previous long-term studies of birds (those lasting at least 5 years) yielded valuable information about the role of environmental factors in the species' success or lack of it. For example, a study on Snow Geese of the Ontario and Manitoba arctic shoreline was the first to discover the damage that this species was doing to large sections of coastal Hudson Bay by observing that Snow Geese were getting smaller and lighter as they started to outstrip their salt marsh food supply and transform this productive ecosystem into a virtual desert.

I was familiar with Semipalmated Plovers, a smallish relative of the noisy and common Killdeer, and knew that they were quite an amenable bird for study. They had a tamer disposition than the Killdeer, a species that inhabits airports, gardens and new housing construction sites in and around Peterborough. I chose to study the plovers in Churchill, Manitoba, where they were quite common.

Since 1987 my students have discovered a great deal about the breeding biology of this species. Allison Rippin Armstrong, one of the first students, discovered that plovers nesting along the Hudson Bay coast had aggregated nesting distributions, whereas plovers nesting inland usually nested by themselves in large gravel opening or river beds in the boreal forest. The birds nesting at inland sites, nested earlier and appeared to incur more predation than the birds at the coast. As a result of this work Michèle Sullivan Blanken decided to test an idea that had originated from a study of African shorebirds: species that nested in sites with low visibility like those inland, exhibited active parental behavior where parents stayed close to the chicks and followed them around during foraging, whereas species that nested in very open sites with greater visibility, like those at the coast, stood a good distance away from the chicks and passively attended their offspring. Michèle found that although birds on the coast chased intruders away from nest sites more, they did not exhibit any different behavioral patterns than those parents at inland sites.

By this time we had enough histories of individually color-banded birds to allow us to look at whether birds would or would not return to their previous nest sites to breed in subsequent years, as well as whether pair bonds were maintained from one breeding season to the next as they are in Canada Geese. Laura Flynn, a student who came from British Columbia to study at Trent, compiled this information and found that divorce rates in this small shorebird were about the same as they are in western human populations (35-45%) and that males, upon return in subsequent breeding seasons nearly always took the same nesting territory as in previous years, whereas females only returned to the same site if they took the same mate.

In contrast to most other plovers, the Semipalmated Plover population does not appear to be declining. In Canada both the Piping Plover and Mountain Plover are endangered and most other species are on their way to becoming so..yes even the seemingly ubiquitous killdeer! The proportion of adults that survives and returns to the breeding grounds from one year to the next is key to determining whether the population will decrease or increase. Debbie Badzinski, a student who completed her undergraduate degree from the University of Western Ontario, used a computer model to determine that this rate was about 71%. Surprisingly, this was about the same value that has been obtained for the other endangered species, so it appears unlikely that adult survivorship alone is responsible for their decline. More likely it is nesting success, the one factor that managers of these threatened and endangered populations have been able to control by reducing the number of nests lost to predators such as raccoons and foxes through use of predator exclosures and, in some cases, predator control.

One of the lowest rates of adult survivorship in Churchill occurred after birds had to endure El Nino winters on their wintering grounds along the southeast coast of the United States. I am now turning my attention to determining how changes in oceanic conditions might affect feeding conditions on tropical and sub-tropical mudflats, and, as a consequence, survivorship of this and other species of migrating shorebirds.

For more information contact Erica Nol enol@trentu.ca