A twenty year study by the Game and Wildlife Conservation Trust (GWCT) shows that red grouse are laying eggs 0.5 days earlier each year, potentially harming their survival chances. As an endemic species, red grouse only exist in the British Isles, where they are an important game bird, and are managed due to loss of their heathland habitat.
The main concern earlier hatching raises for red grouse populations is trophic mismatch. This is where changes in population cycles occur, causing prey and predator species to be ‘out of sync’, with prey populations being lower than previously when predator populations are higher. Predator starvation or reduced survival prospects may result, as less food is available when needed. If red grouse chicks’ prey doesn’t coincide with chick hatching, the young red grouse may be left hungry. The warm weather seems to be driving craneflies – a key chick food – to be emerging even earlier than the chicks. This means even though chicks are hatching earlier, they may not be early enough for their prey and may still miss out. Even worse, early cranefly hatching can mean less survive to lay eggs for the following year.
As is often the case when climate change is considered, the effects on survival are even further complicated. The warmer springs produce more vegetation for red grouse hens to feed on, allowing them to produce more eggs. GWCT have found that hens laying earlier tend to have larger clutches, which could save the birds from decline.
As of yet, no overall effect on red grouse populations has been found.