Factors affecting nest defence in female Canada Geese Branta canadensis

Abstract

The effect of various characteristics of Canada Goose Branta canadensis females and clutch size on their nest defence intensity during incubation was studied in the field during five nesting seasons. Nests were approached by a human, and the leaving distance was measured. Risk-taking in post-encounter behaviour was categorized at three levels. Nesting success was significantly associated with nest tenacity, a variable derived from leaving distance, but not with post-encounter behaviour. Nest tenacity, as well as post-encounter behaviour, differed significantly between individuals. Intensity of post-encounter behaviour, but not nest tenacity, increased with increasing age of the female. Nest tenacity, standardized over the incubation period, increased with increasing clutch size, but postencounter behaviour intensity did not. None of the nest defence variables was correlated with the structural size of the female. Nest tenacity, but not post-encounter behaviour intensity, increased during incubation. Nest tenacity did not differ between early and late breeders, but post-encounter behaviour was more intense in late breeders. There was no evidence of positive reinforcement of nest defence through repeated visits. Nest defence did not differ between lakes, lake types or nest site types, nor was it affected by the distance to the nearest neighbouring nest. The results supported several of the predictions extracted from parental investment theory.

Factors Affecting Flushing Distance in Incubating Female Greylag Geese Anser Anser

“…Sjö berg (1994) obtained similar results for Canada geese Branta canadensis, and Forbes et al (1994) did so for different duck species. Thus, the increased defence intensity during incubation was attributed exclusively to an increased reproductive value of the clutch (Andersson et al 1980, Redondo 1989, Sjö berg 1994.…”

Factors affecting the responses of female Canada Geese to disturbance during incubation

“…Incubating waterfowl respond to the approach of potential nest predators by flushing from their nests. Individual variation in flushing distances (a measure of risk‐taking) has been attributed to variation in the reproductive value of clutches, with shorter flushing distances associated with larger and older (higher value) clutches (Sjöberg , Albrecht and Klvaňa , Quillfeldt et al. , Osiejuk and Kucyński ).…”

“…, Osiejuk and Kucyński ). Female age might also influence flushing distance and return times because older birds likely have more experience and typically have both greater nest success (Brakhage , i.e., current reproductive value), and lower residual reproductive value (Montgomerie and Weatherhead , Redondo ; but see Sjöberg ). Proximate factors, like concealment by vegetation, may also help explain variation in flushing distance.…”

Testing the Terrain Hypothesis: Canada Geese See Their World Laterally and Obliquely

“…This species is gregarious during the nonbreeding season, but it becomes highly territorial when breeding [Mowbray et al, 2002]. Both males and females actively defend their nests [Sjöberg, 1994] and increase their vigilance behavior when in the company of their precocial offspring [Seddon and Nudds, 1994;Caithamer et al, 1996;Fowler and Ely, 1997]. There are many accounts of predation on adult geese by both ground (e.g., coyotes Canis latrans , gray wolves Canis lupus ) and aerial (snowy owls Nyctea scandiaca , golden eagles Aquila chrysaetos , bald eagles Haliaeetus leucocephalus ) predators [Mowbray et al, 2002].…”