This was a year when spring seemed to morph into autumn with very little in between. Autumn arrives officially in September and it’s a time of great change for wild birds.
There are the obvious changes like the departure of summer migrants to the south followed by the arrival of winter migrants from the north. There are also more subtle changes in the diet and behaviour of our resident birds.
For most bird species the breeding season is well and truly over. One exception to this is wood pigeons. They only lay two eggs at a time and compensate for the small clutch size by continuing to do so well into October.
For many other species the end of the breeding season means it is no longer necessary to defend a territory.
Other species begin to form flocks. There seem to be some advantages to living in a flock in the winter --- it probably increases the chances of locating scarce sources of food and decreases the danger of being surprised by a predator. Finches and tits often form quite large flocks and these can contain several related species. Rooks will often mix with jackdaws.
Wood pigeons, because of their late breeding season, don’t normally flock until December in this country.
During the warmer months of the year the diet of most song birds consists mainly of invertebrates — insects, woodlice, spiders, slugs, earthworms. This is a high protein, high energy diet and it’s needed to support them and their offspring through the demands of the breeding season.
With the arrival of autumn the amount of invertebrates declines. They either die off or go into hibernation. Luckily the availability of seeds and berries increases as the meat supply decreases and many small birds are currently switching from being carnivores to becoming vegetarians.
Not all birds adopt this strategy. There are still limited supplies of meat in the form of over-wintering insect larvae and pupae, small spiders in bark crevices and slugs in rotting leaves. Some birds survive by searching out these morsels and refuse the vegetarian option.
Wrens do this, and so do pied wagtails.
But most species, from chaffinches to rooks, are searching stubble fields, hedgerows, waste ground and gardens for seeds, berries and any remaining green shoots.
Many of them survive because of ivy, the berries of which ripen around March and tide them over the ‘hungry gap’ before the insects start to increase in numbers again.
Many, of course, don’t make it through the winter. The death rate, particularly among smaller birds, is enormous as a combination of starvation and hypothermia takes it’s toll. Feeding wild birds in your garden can make a significant difference to this.
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