Risk-taking by female ducks: intra- and interspecific tests of nest defense theory

Abstract

We tested several predictions of nest defense theory by observing variation in flushing distance and probability of nest abandonment within and between six species of waterfowl. In these species, only the females incubate eggs and attend offspring. First, we examined whether flushing distance by females varied in relation to clutch size, stage of incubation, and time of season, after controlling for the number of visits made to nests by observers. Revisits by observers appeared to affect flushing distance by females for reasons unrelated to the relative value of the current clutch. We found that as incubation progressed, females allowed observers to approach more closely before flushing from the nest. In some species, females with larger clutches allowed closer approaches to nests before flushing which was also consistent with nest defense theory. In contrast, time of season (Julian date) did not relate to flushing distance for any species. When species were compared, we found that species with moderate to high yearly mortality and high reproductive output per breeding attempt (e.g., northern shoveler and blue-winged teal) were less likely to abandon nesting attempts and exhibited "riskier" behavior (remained at nests when approached closely by observers) than species that had lower yearly mortality (e.g., mallard). Our results show that flushing distance and patterns of nest abandonment by female ducks conform to several predictions of nest defense 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.…”

“…Alternatively, we may ask how long a parent may delay flushing from its nest, and how this delay (or flushing distance) is balanced between the direct risk to the parent and the risk of revealing the nest position (Albrecht & Klvaňa 2004). Therefore, measurements of flushing distances from an approaching researcher may be used as an appropriate measure of parental investment in cryptically colouredbirds (Forbes et al 1994,Burhans & Thompson 2001, Albrecht & Klvaňa 2004. In this paper, we focused on factors affecting the escape behaviour of incubating female greylag geese Anser anser approached by a human being.…”

Reactions of ground-nesting marine birds to human disturbance in the Canadian Arctic

“…Working at the East Bay field site, Stenhouse et al (2005) found that Sabine's gulls flushed from their nest at approximately 90 m, close to the 100 m average I found for birds at this site approximately one decade later. Kay and Gilchrist (1998) observed that 90% of female common eiders flushed when researchers were 4-8 m from the nest, similar to FID for many other waterfowl species (Forbes et al 1994), but I found that eiders in the high Arctic often initiated flight when people were farther from the nest (~16 m). The species that flushed when humans were farthest from the nest (up to 400 m) was the Ross's gull.…”

“…Previous work has shown that many bird species exhibit species-specific flight initiation distances (FID) (Blumstein et al 2003(Blumstein et al , 2005, meaning that efforts to develop buffer zones around multispecies breeding sites need to consider the reactions of each species to disturbance. Based on earlier work that showed that nest defense ("risk-taking") increases as the breeding season progresses (Forbes et al 1994;Mallory et al 1998), I made two predictions for FID among the sympatrically nesting marine bird species. First, I predicted that sea ducks nesting at the site would have lower FID than the seabirds because female sea ducks undertake all incubation duties and rely on crypsis to avoid detection during incubation, whereas biparentally incubating seabirds rely more on deterrence.…”

Differential investment and costs during avian incubation determined by individual quality: an experimental study of the common eider (Somateria mollissima)

“…Also, nest success rate was reduced when removing one egg from low-quality (four-egg) females. Several studies have shown that birds desert their eggs or chicks when their own body mass is low (Drent 1975;Ankney & MacInnes 1978;Jones 1987;Bustnes & Erikstad 1991;Chaurand & Weimerskirch 1994a,b;Olsson 1997;Kilpi et al 2001;Bustnes et al 2002) or when clutch size is low (Armstrong & Robertson 1988;Forbes et al 1994;Erikstad & Tveraa 1995). Furthermore, brood abandonment rate increased in experimentally reduced clutches of goldeneye ducks, Bucephala islandica (Eadie & Lyon 1998) and in reduced broods in fishes, Aequidens coeruleopunctatus (Sargent 1997;Jennions & Polakow 2001;Vélez et al 2002).…”