Urbanisation and Climate Shape Breeding Phenology in a Subarctic Songbird

Abstract

Abstract

Urbanisation alters ecological conditions in ways that can affect avian reproductive strategies, yet its impacts in high-latitude environments remain underexplored. We investigated how breeding phenology and reproductive success in pied flycatchers (Ficedula hypoleuca) vary across an urban–rural gradient in Arctic Norway, using a combination of long-term data (2007–2018) from a rural site (Lakselvdalen) and comparative data from both rural and urban sites (Tromsø) during 2023–2024. We examined key reproductive metrics—laying date, hatching date, incubation length, clutch size, brood size, and chick loss—and tested their relationships with temperature and precipitation. Results showed earlier laying and hatching over time, closely linked to increasing temperatures. Birds in urban areas laid earlier but exhibited longer incubation periods, delaying hatching and potentially reflecting less favourable microclimatic or ecological conditions. While clutch size increased in warmer years, brood size and fledging success were relatively stable. Chick loss was lower in the urban site, possibly due to reduced predation or disturbance. Our findings suggest that reproductive timing in Arctic flycatchers is advancing with climate warming but that urban conditions may introduce additional constraints, influencing incubation behaviour and reproductive outcomes.

Abstract

Urbanisation alters ecological conditions in ways that can affect avian reproductive strategies, yet its impacts in high-latitude environments remain underexplored. We investigated how breeding phenology and reproductive success in pied flycatchers (Ficedula hypoleuca) vary across an urban–rural gradient in Arctic Norway, using a combination of long-term data (2007–2018) from a rural site (Lakselvdalen) and comparative data from both rural and urban sites (Tromsø) during 2023–2024. We examined key reproductive metrics—laying date, hatching date, incubation length, clutch size, brood size, and chick loss—and tested their relationships with temperature and precipitation. Results showed earlier laying and hatching over time, closely linked to increasing temperatures. Birds in urban areas laid earlier but exhibited longer incubation periods, delaying hatching and potentially reflecting less favourable microclimatic or ecological conditions. While clutch size increased in warmer years, brood size and fledging success were relatively stable. Chick loss was lower in the urban site, possibly due to reduced predation or disturbance. Our findings suggest that reproductive timing in Arctic flycatchers is advancing with climate warming but that urban conditions may introduce additional constraints, influencing incubation behaviour and reproductive outcomes.