When summer comes, the pace of bird life increases rapidly. Foraging becomes a race as young chicks grow, and all bird species suffer heavy mortality at this time. Each species has its characteristic schedule of breeding activities to be completed before autumn.
Birds do not waste summer, as this is when they are busiest. Summer is short, and most adult pairs struggle to produce young birds. The number of young that eventually survive to breed is always a small fraction of the number of eggs laid, as summer is particularly hazardous.
Whatever the day-to-day risks, the limiting factor is time, so the breeding season follows a tight schedule.
How Plants Help Birds In Summer
Summer foliage is exploited as cover for hiding nests by dozens of species that seek to raise their young within trees, bushes, or on the ground among the grass and other low plants.
As May progresses, hedges and thickets become impenetrable, and jays and magpies experience greater difficulty finding unguarded nests to plunder.
One of the factors that permits this quick growth of new leaves is the increased day length of summer. Throughout May, June, and July, the sun is high for over 15 hours a day. Such long days give plenty of time for birds to forage, both for themselves and for their young.
What Do Migrant Birds Do In Summer?
Plants are the primary food producers, and the small animals that thrive on their growth produce protein-rich food at the secondary level, the herbivorous animals.
A large amount of this is flying insects, and it is these that many species of insectivorous migrant birds feed on. Warblers, chats, flycatchers, swifts, swallows, martins, nightjars, wagtails, and others migrate annually, so by the end of May, the total number of breeding birds grows rapidly.
By the end of August, these may have raised enough young to produce a total of over 500 million birds in a country the size of the United Kingdom
Bird Deaths In Summer
Studies show that more dead birds are found in summer than in winter. Young birds are vulnerable, but even adults can fall foul to summer.
Those reporting the discovery of their remains often find evidence of the causes of death, such as cats, traffic, and collisions with windows.
Having made a nest, parent birds will return to it at regular intervals, easily attracting the attention of cats and, if a road lies en route, increasing the risk of being hit by traffic. Many summer visiting birds die, though we know little of the severity of dangers that face such birds on migration or in their winter habitats.
As for the fledglings, many die within a month of birth. Their instinct for danger is not yet reinforced by practical experience, their flight is often weak, and they must call their parents to demand food at regular intervals.
Breeding Season
For the birdwatcher interested in breeding behavior, observing the schedules followed by different species is fascinating.
Among the earliest breeders are the ground-feeding birds, such as the song thrush and the blackbird. Taken as a group, the ground feeders are not selective in the foods they eat, though animals are generally predominant in summer rather than seeds, nuts, or fruits.
They will eat worms, slugs, millipedes, and other similar animals in the soil. This kind of food is less seasonal than most, with good quantities available in milder phases of winter, and once spring comes, there is enough food for some blackbirds to start laying eggs.
Laying Eggs At The Right Time
Different birds breed according to different schedules. The first six birds here represent small species: ground-feeders breed earliest, followed by insectivores (except migrants like the swallow) and then seed-eaters. Among birds of prey, two contrasting strategies are shown: the flexible timing of the barn owl and the fixed timing of the sparrowhawk. To complete the picture, two seabirds are shown.
Besides the problems large ground feeders such as rooks experience if dry weather in July hardens the earth, the soil and its surface continue to nourish small animals throughout the summer.
Both blackbirds and song thrushes can continue their breeding over a long season and may raise three or even four broods, the last becoming independent as late as September.
Insect-eaters do not start their season as early as the song thrush and blackbird, waiting at least until late April. May is generally when the winter moth caterpillars hatch in their millions, and blue tits and other members of the tit family choose to mate at the precise time when their single brood of young will develop in time to thrive on these caterpillars.
The breeding season of swallows, swifts, and martins is determined by the time these migrants arrive and their dependence on flying insects. Their first eggs are laid from mid or late May onwards.
Seed-eaters are generally the latest breeders, as seeds do not become abundant until late May. The first broods of finches and buntings can be expected to be flying from this time onwards, feeding from each plant species in turn as the seeds ripen.
What Do Birds Of Prey Do In Summer?
Among the larger birds are those that feed by swooping down upon other birds or on terrestrial animals: the predators. Within this diverse group, timing strategies of breeding vary.
Barn owls feed on many kinds of prey, from mice and birds to earthworms and large insects. They can take whatever is available at the time, feeding entirely on birds, often specializing in particular species.
Males, which are smaller, will frequently catch finches, sparrows, buntings, or tits, while the female hunts thrushes and starlings. Like barn owls, the sparrowhawks are single-brooded, but their breeding season must synchronize with the peak availability of food. Their young are in the nest from mid-May to July or August.
Young Birds
The chicks of most waders and gulls are relatively mature when they hatch and can see and run about when only hours old. This does not shorten their breeding season, with incubation and fledging times of three to four weeks and five to six weeks, respectively, being typical.
This enables them to be flexible in the timing of their breeding. Though pairs raise only one brood, they can choose to lay their clutch of eggs in almost any month of the year. Most are incubating in April and May, the young taking wing some ten weeks later.
