Nest and brood stage association between ducks and small colonial gulls in boreal wetlands

201

Nuoret haapanasaaliissa – saalisosuuden muutokset ja säätekijöiden merkitys vuosien välisessä vaihtelussa

Summary: The proportion of juveniles in the hunting bag of Eurasian wigeon in Finland – long-term changes and the role of climatic conditions in explaining among-year variation The proportion of first-year birds in annual wing samples provided by hunters has been used as a measure of breeding success in waterfowl. The proportion of first-year birds in the wing samples of Eurasian wigeon Mareca penelope from Denmark and the United Kingdom shows a long-term decline, probably reflecting a decrease in breeding success. However, previous studies report conflicting results in the relationship between variation in the proportion of first-year birds and variation in climatic conditions. Here, we summarize main results of a study (Pöysä & Väänänen 2018) in which we used wing data of hunter-shot Eurasian wigeon from Finland to study whether the proportion of first-year birds shows a similar long-term decline and whether among-year variation in the proportion of young is associated with variation in climatic conditions. In addition, we discuss possibilities to improve sustainable hunting of ducks in Europe based on stable isotope analysis of wing samples from hunter-shot birds. We found a long-term decline in the proportion of first-year birds (Fig. 1). The proportion of young also varied considerably between years, but this variation was not associated with weather or the climatic variables considered for the breeding and wintering periods. This was the case particularly when controlling for common trend (year) in the response variable and explanatory variables (Table 1). More research is needed concerning factors that affect long-term changes and annual variation in the proportion of young in the hunting bag and on the suitability of this index to measure productivity in ducks.Peer reviewe

Estimating production in ducks : a comparison between ground surveys and unmanned aircraft surveys

We tested the use of unmanned aerial systems (UAS) in duck brood surveys in boreal wetlands in Finland. We performed brood surveys at the same wetlands concurrently with ground-based point counts and using a UAS (multicopter; drone counts) equipped with a camera that produced high-quality images for identification of broods and ducklings. The number of broods did not differ between point counts and drone counts in three duck species, the mallard (Anas platyrhynchos), common teal (Anas crecca), and common goldeneye (Bucephala clangula). The number of ducklings was higher in drone counts than in point counts in the common teal, but no such difference was found in the mallard and common goldeneye. UAS-based images seem to be useful for estimating numbers of both broods and ducklings for different duck species, although the manual processing of images is labor intensive.Peer reviewe

Duck-fish competition in boreal lakes - a review

201

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

Avian species respond to ecological variability at a range of spatial scales and according to life history stage. Beaver dams create wetland systems for waterbirds that are utilized throughout different stages of the breeding season. We studied how beaver?induced variability affected mobile pairs and more sedentary broods along with the production of Common Teal Anas crecca at the patch and landscape scale on their breeding grounds. Beavers Castor spp. are ecosystem engineers that enhance waterfowl habitats by impeding water flow and creating temporary flooding. Two landscapes in southern Finland with (Evo) and without (Nuuksio) American Beavers Castor canadensis were used in this study. To investigate the patch?scale effect, pair and brood densities along with brood production were first compared at beaver?occupied lakes and non?beaver lakes in the beaver landscape. Annual pair and brood densities/km shoreline and brood production were compared between beaver and non?beaver landscapes. Facilitative effects of beaver activity were manifest on brood density at both patch and landscape scales: these were over 90 and 60 percent higher in beaver patches and landscapes, respectively. An effect of beaver presence on pair density was only seen at the landscape level. Pair density did not strongly affect brood production, as shown earlier for relatively mildly density?dependent Teal populations. Because the extent of beaver flooding was a crucial factor affecting annual Teal production in the study area, we infer beaver activity has consequences for the local Teal population. Ecosystem engineering by the beaver could therefore be considered as a restoration tool in areas where waterfowl are in need of high?quality habitats. This article is protected by copyright. All rights reserved.Peer reviewe

Avohakkuiden vaikutus maassa pesivien lintujen pesäpredaatioon – koepesätutkimus

Summary: Effect of forest clear-cutting areas on nests depredation of ground nesting birds – an artificial nest experiment. Nest predation is one of the most important factor affecting bird’s offspring production. However, nest predation is not very well studied, and the real role of different predator species predating ground nesting birds’ nests is still widely unclear. We especially need more information of nest predation and predators in different habitat types, such as boreal forests. The need is especially urgent, because there has been a fast increase of alien predator populations in Finland and Europe during the past decades. Alien predators pose a potential enhanced risk to many native bird species, such as forest grouses. Here, we study the nest depredation of ground nesting birds in barren coniferous forests, which are relatively far away from human settlements and fields. There are also only small number of lakes and ponds in our study area. The area is situated in the middle part of Finland in Suomenselkä region. We created 156 artificial nests with four pheasant eggs in low densities in 2018 and monitored them for seven days after construction using wildlife cameras to record whether nest predators visit and prey upon the nests. From the 156 artificial nest 26 (17 %) were depredated: in clear-cutting area 10 (19 %), forest edge 9 (17 %) and 7 (13 %) inside forests. The most common nest visitors were avian predators, which took 19 nets (raven Corvus corax 10, great tit Parus major 5, jay Garrulus glandarius 3 and great spotted woodpecker Dendrocopos major 1 nest). Mammals depredated only 2 nest (red fox Vulpes vulpes 1 and moose Alges alges 1 nest. In five nest depredation cases we did not succeeded to identify nest predators because of camera failure. All in all, nets depredation rate on barren coniferous forest seem to be relatively low. We used GLMM (Generalised linear mixed model) to find explanatory fosters explaining nest depredation risk in two different landscape scale (250 m and 500 m wide radius around nets). Results indicate that 250 wide buffer area around nest may explain better nest depredation risk, but results were not statistically significant. In our best model small forest road and electric power line areas explain best nest depredation risk (250 m radius). The size of the clear-cut did not affect the nest probability to become depredated. Even though we have relative big number of artificial nest, only few were depredated and thus the sample size was too low to find significant results. Therefore, more data is needed to find more precise depredation risk level of ground nesting birds in barren forests. Absence of raccoon dog was a bit surprising, because it is the most common nest predator in an agricultural–forest landscape and near lakes and ponds. Our results suggest that nest depredation risk is low in forests far from human settlements and fields.Peer reviewe

Compensating freshwater habitat loss-duck productivity and food resources in man-made wetlands

Correction Volume 68 Issue 3 Article Number39 DOI 10.1007/s10344-022-01591-w Published JUN 2022The number of wetlands in Europe decreased by more than 60% by the 1990s compared with the beginning of the twentieth century. Man-made wetlands may be an effective way to compensate for the loss and degradation of freshwater ecosystems. This loss impacts the populations of declining duck species, partly due to a lack of suitable breeding opportunities. In this study, we evaluated duck productivity and invertebrate abundance in 13 man-made Finnish wetlands that were created for waterbirds. Our findings revealed that man-made wetlands have higher duck production than average natural boreal lakes. High invertebrate levels were a key factor that positively correlated with duck pair density, brood density, duckling density of the common teal (Anas crecca), and duck density during the post-breeding period. Our results suggest that man-made wetlands are a useful tool for increasing duck productivity. For upholding this status in the long term, appropriate management should involve maintaining sufficient invertebrate levels.Peer reviewe