Vegetation structure influences predation rates of early nests in subarctic breeding waders

Abstract

Ground‐nesting species are vulnerable to a wide range of predators and often experience very high levels of nest predation. Strategies to reduce nest vulnerability can include concealing nests in vegetation and/or nesting in locations in which nests and eggs are camouflaged and less easy for predators to locate. These strategies could have important implications for the distribution of ground‐nesting species and the success rates of nests in areas with differing vegetation structure. However, the factors influencing the success of nest concealment and camouflage strategies in ground‐nesting species are complex. Here we explore the effects of local vegetation structure and extent of nest concealment on nest predation rates in a range of ground‐nesting, sympatric wader species with differing nest concealment strategies (open‐nest species: Oystercatcher Haematopus ostralegus, Golden Plover Pluvialis apricaria and Whimbrel Numenius phaeopus; concealed‐nest species: Black‐tailed Godwit Limosa limosa, Redshank Tringa totanus and Snipe Gallinago gallinago) in south Iceland, in landscapes that comprise substantial variability in vegetation structure at a range of scales. We monitored 469 nests of these six wader species in 2015 and 2016 and ~40% of these nests were predated. Nest predation rates were similar for open‐nest and concealed‐nest species and did not vary with vegetation structure in the surrounding landscape, but nest‐concealing species were ~10% more likely to have nests predated when they were poorly concealed, and the frequency of poorly concealed nests was higher in colder conditions at the start of the breeding season. For concealed‐nest species, the reduced capacity to hide nests in colder conditions is likely to reflect low rates of vegetation growth in such conditions. The ongoing trend for warmer springs at subarctic latitudes could result in more rapid vegetation growth, with consequent increases in the success rates of early nests of concealed‐nest species. Temperature‐related effects on nest concealment from predators could thus be an important mechanism through which climate change affecting vegetation could have population‐level impacts on breeding birds at higher latitudes.

Shorebird Reproductive Response to Exceptionally Early and Late Springs Varies Across Sites in Arctic Alaska

“…The presence of higher numbers of alternative prey may promote increased numbers of breeding shorebirds (Blomqvist et al, 2002;Robinson et al, 2014) and mitigate the risk of predation on their nests (Bêty et al, 2002;Smith et al, 2007;McKinnon et al, 2012, but see Weiser et al, 2018a. Persistent spring snow cover may also directly increase the predation of shorebird nests, as late-melting snow limits the area available for nesting, allowing predators to concentrate their search effort (Byrkjedal, 1980;Meltofte et al, 1981;Machín et al, 2019), and the growth of vegetative cover is phenologically delayed making nests more obvious (Laidlaw et al, 2020). However, late-melting snow may also lead to synchronous nesting that could dilute the risk of predation to any one nest .…”

Diel timing of nest predation changes across breeding season in a subtropical shorebird

“…The lack of overall differences between day and night predation are described, but not formally tested, from the subarctic and arctic regions (Laidlaw et al., 2020 ; Tulp & Schekkerman, 2001 ), and anecdotal evidence suggests that the lack of diel pattern in nest predation may be found also in species from regions with a similar composition of predator community (Kosztolanyi et al., 2009 ; Shkedy & Safriel, 1992 ). Moreover, around the clock predation is common in ground‐nesting passerines (Pietz et al., 2012 ; Praus & Weidinger, 2010 ; Weidinger, 2010 ), as well as in small shorebirds, that do not actively deter predators (Ekanayake, Weston, et al., 2015 ; Macdonald & Bolton, 2008 ).…”

“…We considered nests as hatched ( N = 312), when at least one chick hatched, based on observations of (i) at least one chick on or around the nest during the final nest‐check ( N = 197 nests), (ii) color‐marked parents guiding chicks after the final nest visit ( N = 36 nests), or (iii) small (≤ 5mm) eggshell pieces in the nest that result from a chick chipping its way out of its egg ( N = 79; Brown et al., 2014 ; Mabee et al., 2006 ). The use of eggshell pieces has been used to define successfully hatched nests in other shorebird species (Kentie et al., 2015 ; Laidlaw et al., 2020 ). Importantly, we ringed 233 chicks whose identity was unknown as they were found away from nests.…”

“…While nest predation is relatively well studied in general, our knowledge is biased toward the Northern hemisphere temperate and arctic regions (Bulla et al., 2019 ; Freeman et al., 2020 ; Kubelka, Šálek, et al., 2018 ; Unzeta et al., 2020 ), which hampers global comparative analyses. Moreover, regardless of the region, we know fairly little about when within a day nests are predated (Tulp et al., 2001 ; hereafter “diel timing of nest predation”; Praus & Weidinger, 2010 ; Weidinger, 2010 ; DeGregorio et al., 2015 ; Brynychová et al., 2020 ; Laidlaw et al., 2020 ), perhaps because it requires continuous nest monitoring (Pietz et al., 2012 ; Weidinger, 2006 ).…”

Macroecology of North European Wet Grassland Landscapes: Habitat Quality, Waders, Avian Predators and Nest Predation

“…Our results in the north European macroecological gradient are supported by other comparative studies. In Iceland, where our nest predation experiment failed, Laidlaw, et al [97] monitored 469 wader nests in 2015 and 2016, of which 40% were predated. Groen, et al [98] and Kentie, Both, Hooijmeijer and Piersma [33] also demonstrated lower wader nest predation patterns (daily predation probability of 0.025) in favourable semi-natural grasslands compared to unfavourable intensified grassland monocultures (0.045) in Friesland, Netherlands.…”