Tómas G. Gunnarsson

Degradation of natural and semi‐natural habitats is often initiated and facilitated by expansions in anthropogenic infrastructures. Identifying and reducing the impact of anthropogenic structures on the wildlife that these habitats support is vital for biodiversity conservation. In Iceland, the number of summer houses has increased over the past two decades, from ~10 000 to 15 000, and >7000 additional plots for summer house construction have been approved. Most of this housing infrastructure development is in the Icelandic lowlands, which support internationally important populations of several ground‐nesting bird species. To explore the effects of summer house infrastructure on the distribution of ground‐nesting birds, we conducted surveys at 292 points within 71 sites with varying density of houses and associated infrastructure (tracks, decking, etc). Significant reductions in abundance with increasing housing density occurred in five (Golden Plover ( Pluvialis apricaria ), Black‐tailed Godwit ( Limosa limosa ), Redshank ( Tringa totanus ), Whimbrel ( Numenius phaeopus ) and Meadow pipit ( Anthus pratensis )) of the seven study species, while one species (Snipe ( Gallinago gallinago )) showed no change and one (Redwing ( Turdus iliacus )) increased. The differences in abundance between plots with no houses and plots with high house densities (>0.5 houses ha −1 ) ranged from 34 to 95%, despite the housing infrastructure covering only ~6% of the area of these plots. These findings suggest that even relatively low densities of anthropogenic structures in natural or semi‐natural areas can have substantial impacts on wildlife in the surrounding areas and highlight the urgent need for effective planning regulations to limit the expansion of anthropogenic structures into currently undisturbed habitats, particularly in areas of high biodiversity value.

Advancing breeding phenology is a commonly observed response to climate warming among bird species, potentially in response to shifts in the phenology of key resources. However, for migratory birds breeding at high latitudes, their capacity to breed earlier may be constrained by the time available between arrival on the breeding grounds and nesting, especially for later‐arriving individuals. This may have consequences for productivity, as early laying is often linked to higher breeding success, particularly in such seasonal environments. We investigated how migratory arrival timing influences subsequent timing of breeding, in particular whether the time between arrival and laying (arrival–laying gap) varies with arrival date, and if later‐arriving individuals are able to catch up with early‐arriving conspecifics. We tracked individual Icelandic Black‐tailed Godwit Limosa limosa islandica with GPS and PTT tags for one to two complete breeding seasons between 2013 and 2022. After arrival in Iceland, most Godwits visited their breeding territory within 5 days, though this interval was longer for earlier‐arriving birds. The total gap between arrival and laying was also longer for earlier‐arriving birds, such that laying date did not vary significantly with arrival date. These results suggest that, despite individual consistency in migratory phenology, subsequent timing of nesting is probably influenced by other factors, such as mate arrival timing and/or annual variation in environmental conditions. Regular pre‐nesting visits to the breeding territory may indicate that Godwits are able to monitor such factors closely and to nest early when conditions allow, but a larger sample of individuals and years is needed to assess whether early‐arriving individuals contribute disproportionately to population‐level advances in breeding phenology. Widespread tracking with high temporal and spatial resolution helps improve our understanding of phenological variation during the breeding season and its consequences for productivity and variation in juvenile phenology.