Woodland management for birds: Birds and woodlands in Wales
or a combination. However, little is known about their wintering ecology, and conditions are probably highly variable, having different impacts on different species.
Climate change on the breeding grounds
The British climate has changed markedly in the last 30 years; winters becoming wetter and milder, and summers drier. Breeding phenology has altered with an advance in egg-laying times and the active growing season of plants. One area of concern focuses on the ability of birds to adapt to climate change. Many insectivorous birds depend for a short period on butterfly and moth larvae in the breeding season, therefore a critical issue is whether the timing of breeding could
become decoupled from the availability of food supplies. Some resident birds are able to synchronise hatching dates with peak food supplies. This situation may be more serious for long-distance migrants; pied flycatchers have been shown to advance laying dates in response to increasing spring temperatures, yet they are not returning any earlier from Africa. The timing of migration in some species is determined by internal genetic signals that are not altered by climate change, therefore long-distance migrants may be unable to adapt the timing of their migration to match periods of habitat optimality on the breeding grounds. An increase in the number of hot days in summer and the frequency of droughts may reduce moisture in woodland soils, which may affect the availability of soil invertebrates to foraging woodcock.