Balancing between predation risk and food by boreal breeding ducks

Abstract

1. Wetlands belong to the globally most threatened habitats, and organisms depending on them are of conservation concern. Wetland destruction and quality loss may affect negatively also boreal breeding ducks in which habitat selection often needs balancing between important determinants of habitat suitability. In Finland duck population trajectories are habitat-specific, while the reasons behind are not known. 2. In this research, the balance of nest predation risk and invertebrate food abundance in boreal breeding ducks was studied in Finland at 45 lakes and ponds in 2017 and 2018. Nest predation experiments were conducted with artificial nests followed by wildlife cameras during seven days. Invertebrates were sampled from the study water bodies using emergence and activity traps. Duck pairs and broods were also surveyed from these and 18 additional water bodies. 3. The wildlife camera results indicate that predation risk was higher in the water bodies surrounded by agricultural land than forestland. Ponds (seasonal, beaver and man-made) had lower nest predation risk and they were also more invertebrate-rich habitats than permanent lakes. In addition, artificial nests further away from water bodies had higher survival than shoreline nests. Habitat use of duck pairs (prior to nesting) was not associated with invertebrate food, but duck broods preferred habitats rich in food. 4. High nest predation pressure in shorelines of especially agricultural landscapes may contribute the declining population trends of ducks in Finland. Controlling predators would be an important conservation action to improve duck breeding success. This research underlines the benefits of the availability of different water body types for the breeding ducks. There is an urgent need to pay attention to protecting seasonal ponds, while the lack of flooded waters may be mitigated by favouring beavers or man-made ponds.

Riding the wetland wave: Can ducks locate macroinvertebrate resources across the breeding season?

“…In contrast, reservoirs and basin wetlands consistently held water toward the end of the breeding season when broods congregated to forage. Semi‐permanent wetlands also typically had more open water, which may have allowed birds to use observable SAV as an indication that a given wetland may provide food for their ducklings and find refuge in large water bodies away from edges and dense cover (Behney et al., 2018; Fredrickson & Reed, 1988; Holopainen et al., 2024). Indeed, although energy density best predicted duckling density of all focal species but gadwall (Table 2), the relationships were negative and imprecise (Figure 7).…”

“…The amount of food in a given wetland is not always directly proportional to the observed density of waterfowl using that wetland, and many components of the habitat may preclude waterfowl from freely distributing themselves according to food availability (Brasher et al, 2007;Hagy & Kaminski, 2015;Holopainen et al, 2024;Paasivaara & Pöysä, 2008). In this system, agricultural wetlands were flooded and dried according to production needs, often resulting in dry, mowed fields during the peak of brood-rearing (Duebbert & Frank, 1984;McVey, 2011).…”

“…Ducks have been shown to prospect for sites in advance of nesting that appear to provide high‐quality foraging habitat for themselves and their broods (Casazza et al., 2020; Eadie & Gauthier, 1985). Whether those sites remain high‐quality is a function of the diversity of the forage resource community, the degree to which that community pulses ephemerally, and a myriad of biotic and abiotic factors related to safety (Holopainen et al., 2024; Recer et al., 1987) and wetland plant configuration (Kaminski & Prince, 1981; Masto et al., 2022). Breeding waterfowl must be able to either select habitats where there is temporal stability in the resource or must be able to track resource pulses over space and time to ensure that their life‐history events overlap with the life stages at which resources are available (Deacy et al., 2018; Nummi et al., 2015).…”