Breeding in the stable boreal landscape: lake habitat variability drives brood production in the teal (Anas crecca)

Abstract

1. Boreal forest lakes are normally considered stable environments, but from a duck's point of view, both resource abundance and habitat quality in the lakes may differ from 1 year to another. Duck species differ in their flexibility to respond to variation in environmental factors, such as habitat quality, habitat variability and weather. Anas crecca, the common teal, has been suggested to be a species that can readily colonise newly formed habitat. 2. We studied the effect of habitat quality (invertebrate food resources, amount of spring flood, beaver flood abundance, predation pressure), weather (temperature, precipitation, timing of ice breakup) and pair abundance on breeding success of teal at the landscape scale in Southern Finland. We used 20 years of data (1989-2008) from a study area consisting of 50 lakes. This is typical boreal breeding area for the teal, whose population size is markedly variable. We express breeding success as number of broods in two different age classes. 3. The number of broods in both age classes was explained well by habitat quality, but different variables seem to operate during different phases of the breeding season. Increases in abundance of breeding pairs and of food led to increased production of younger broods. Habitat factors including food and flood abundance were the most important predictors for older broods, which are the more influential in terms of recruitment. These factors manifested in an age-specific manner, highlighting the importance of comprehensive breeding time surveys of boreal breeding ducks to understand variation in their recruitment. 4. Our research underlines the importance of high-quality habitats for breeding teal populations in the boreal forest landscape. The existence of these habitats depends substantially on human actions, such as managing beaver populations and preserving seasonal pond habitats.

The effect of beaver facilitation on Common Teal: pairs and broods respond differently at the patch and landscape scales

“…Secondly, and possibly more importantly, other flooded areas in riparian forests, namely seasonal wetlands created by melting snow, have been shown to be suitable for foraging during the pairing season (Paton , see also Holopainen et al . ). This may dilute the Beaver flowage effect during spring, when large amounts of flooded shores and vernal pools are available.…”

“…The amount of Beaver flooding was also the most important factor affecting yearly Teal production in the area, among such environmental factors as food abundance (Holopainen et al . ). This could also be the reason why the brood density varied more in the Beaver landscape.…”

“…The ducks are the most difficult to detect in Beaver ponds (see Holopainen et al . ) and thus the numbers of birds found there are conservative. In both landscapes, all wetlands inside a certain area were surveyed.…”

Assessing breeding duck population trends relative to anthropogenic disturbances across the boreal plains of Canada, 1960–2007

“…Roads share some attributes of seismic lines and pipelines, in that they are linear features contributing to edges and fragmentation of forested areas, potentially facilitating movement of predators. Furthermore, they also have the potential to block stream systems when not built properly and thereby function as analogs to beaver dams, which can benefit waterfowl (Martell et al 2006, Holopainen et al 2014. Thus, developing a priori hypotheses of relationships between roads and population trajectory of ducks was difficult.…”

“…Thus, there may be top-down (predation-related) and bottom-up (hydrological) processes related to resource extraction development that could be limiting waterfowl populations (Slattery et al 2011). However, hydrologic impairment caused by roads may be analogous to beaver dams (Martell et al 2006, Holopainen et al 2014, creating more open water habitat than would be present otherwise, and so uncertainty remains about the net effects of roads, and other industrial infrastructure, on waterfowl population trends.…”