Multi-scale habitat selection affects offspring survival in a precocial species

Abstract

In theory, habitat preferences should be adaptive. Accordingly, fitness is often assumed to be greater in preferred habitats; however, this assumption is rarely tested and, when it is, the results are often equivocal. Habitat preferences may not directly convey fitness advantages if animals are constrained by tradeoffs with other selective pressures like predation or food availability. We address unresolved questions about the survival consequences of habitat choices made during brood-rearing in a precocial species with exclusive maternal care (mallard Anas platyrhynchos, n = 582 radio-marked females on 27 sites over 8 years). We directly linked duckling survival with habitat selection patterns at two spatial scales using logistic regression and model selection techniques. At the landscape scale (55-80 km(2)), females that demonstrated stronger selection of areas with more cover type 4 wetlands and greater total cover type 3 wetland area (wetlands with large expanses of open water surrounded by either a narrow or wide peripheral band of vegetation, respectively) had lower duckling survival rates than did females that demonstrated weaker selection of these habitats. At finer scales (0.32-7.16 km(2)), females selected brood-rearing areas with a greater proportion of wetland habitat with no consequences for duckling survival. However, females that avoided woody perennial habitats composed of trees and shrubs fledged more ducklings. The relationship between habitat selection and survival depended on both spatial scale and habitats considered. Females did not consistently select brood-rearing habitats that conferred the greatest benefits, an unexpected finding, although one that has also been reported in other recent studies of breeding birds.

The adaptive value of habitat preferences from a multi-scale spatial perspective: insights from marsh-nesting avian species

“…On the other hand, determinants of occurrence at smaller spatial scales may be related to particular habitat structure selected to reduce predation risk (Martin, 1998). Such a pattern was found in mallards ( Anas platyrhynchos ), where duckling survival was linked to selection of wetlands by brood-rearing adults at the landscape scale, but not to local-scale preferences (Bloom et al, 2013). Nevertheless, the mechanisms that link survival of chicks to landscape scale attributes have to be further investigated.…”

“…In birds, decisions related to the selection of the breeding site are usually determined by the availability of critical resources, such as food (Crampton & Sedinger, 2011; Barea, 2012) and refuge from predators (Forstmeier & Weiss, 2004; Forsman et al, 2013), which in turn may strongly affect multiple fitness outcomes. Occupying high-quality habitats determine, in general, higher fitness indices for clutches (nest survival, clutch size, clutch mass; Martin, 1998), fledglings (offspring mass and survival; Bloom et al, 2013; Germain et al, 2015), and adults (survival of individual birds, seasonal reproductive success, numbers of nesting attempts; Chalfoun & Martin, 2007). In response to patchiness and hierarchical structure of the environment, birds tend to recognize and select their habitat at several spatial scales (Fuller, 2012).…”

Selecting habitat to what purpose? The advantage of exploring the habitat–fitness relationship

“…In ungulates, the habitat selected by a female when establishing its home range and during its daily movements is crucial to the survival of its calf (McLoughlin et al 2006(McLoughlin et al , 2007. In birds, selection of a good nest site is most important to chick survival (Badyaev 1995, Aldridge and Boyce 2007, Sandercock et al 2015, even though in some species adult habitat selection also plays a role in the survival of their offspring (Bloom et al 2013). In carnivores, the habitat at the den is essential for pup/cub survival, but adult habitat selection is also important.…”

“…The collective impression of those studies has been characterized as “equivocal” (Bloom et al. ). The equivocal results of those studies are likely, and in part, the consequence of two complicating circumstances.…”

“…Evaluations of the importance of habitat selection on realized fitness are also exemplified by numerous assessments of the relationship between nest site selection for birds and some aspect of RS, for example, nest survival (Badyaev 1995, Aldridge and Boyce 2007, Sandercock et al 2015, Gibson et al 2017. The collective impression of those studies has been characterized as "equivocal" (Bloom et al 2013). The equivocal results of those studies are likely, and in part, the consequence of two complicating circumstances.…”