Those of you who watched this year’s SpringWatch will have noticed birds hedging their bets on whether to breed early and risk a cold spring, or leave it to later in the season.
Over the years I’ve noticed that generally our garden birds are breeding earlier and earlier in response to the mild weather we normally enjoy from March onwards. Gone are the days of my childhood when it wasn’t an uncommon sight to see blankets of snow several feet deep right the way from November to March.
The latest information gathered in the Nest Record Scheme, which is run by the British Trust for Ornithology (BTO)* shows that a significant number of species are breeding earlier than they did when records began in the 1960s. This is thought to be caused by climate change as temperatures have increased over time.
Regardless of the cause, there is strong evidence to suggest that over 35 species of bird are laying their eggs between one and 27 days earlier, on average, than in the mid 1960s.
The garden bird species reacting best to the changes in temperature are the Greenfinch, Robin, Blue Tit and Magpie. However, depending on the year, this may or may not be a good evolutional tactic.
If birds lay early and it is a particularly cold spring (as it is at the moment), there is a change that natural food sources will be thin on the ground, causing a food shortage. This can have a big impact on population levels at this critical time of year when young chicks are being reared.
It’s also a good idea for households to leave out some food for birds, regardless of the time of year. It provides them with a guaranteed meal, which can very often mean the difference between a population boost or a further decline.