These long periods of sub-zero temperatures are really hard for the reserve’s small birds.
Birds are particularly vulnerable in a harsh winter; it is believed that the terrible winter of 1962/63 killed half of Britain’s wild bird population. Small insect eaters like wrens and goldcrests suffered particularly badly, and the kingfisher population fell by 90% because ponds and lakes were frozen solid for weeks; even the sea froze.
Researchers have found that after a long cold winter’s night, blue tits and great tits are some 5% lighter at dawn than they were when they went to roost. The lower the night time temperature and the longer the night, the more weight they lose. Last night was fourteen and a half hours long and the temperature fell to -2°C.
Blue tit by Simon Knight and great tit by DKG, both pictures taken in the park
The RSPB says that a blue tit, which weighs about eleven grams, needs to eat at least one calorie per gram of its body weight, each day; more, if it is to survive extended periods of freezing weather. Eleven calories doesn’t sound much, but it is the equivalent of about three hundred small insects; that is a lot of foraging in less than ten hours of daylight when most insects are either hidden away in hibernation or in some quiescent stage of their life cycle.
Goldfinches and a blue tit sometimes need the extra calories provided by a bird feeder.
Your garden bird table may be a life-saver, providing essential support to tits and finches in these hard times. Add high calorie foods to your feeders: fats, peanuts, sunflower seeds and, if you know where to get them during lockdown, mealworms. Be careful about kitchen scraps, though: salt is very bad for birds and even a little can upset their metabolism. Don’t forget fresh water; so many of the places where birds usually go to drink will be frozen over today.
Wrap up warm and go carefully. Stay safe.