There is a gradual lulling of the sounds of summer as birds now find it not quite so important to declare their territorial boundaries. Most disputes over territory were settled some time ago although in many cases, cock blackbirds and thrushes have resumed song whilst their mates start all over again incubating their next clutches.
Other birds are kept busy feeding their fast growing broods. For example, it has been recorded that in a single day a pair of great tits brought their brood no fewer than 900 meals ….. one every daylight minute.
The fact is that tits notoriously go in for large families – sometimes into double figures – and further, that tits are very rapid developers requiring a mere fortnight to be on the wing Thus, their growth rate and their requirement for food is astonishing. Many of the smaller birds follow this pattern – large and a rapid turnover of clutches and a consequential need for the youngsters to become self-sufficient in as short a space of time as possible.
The contrast between this pattern and that followed by birds of prey is considerable. One clutch is quite enough for our predatory birds and in general their clutches are relatively small. The incubation period also differs – a mere fortnight for many small birds whilst a month or longer is the norm for most predators. Even then, there is frequently a long feeding period required before the offspring are capable of going it alone.
Therefore, it did not surprise me to find myself gazing skyward at the weekend to admire a pair of circling buzzards. I watched them come off the cliff face, where they nest, and soar into a brilliant blue sky flecked with massive pillars of frothy white clouds. As they drifted across the blazing sun their plumage seemed to be fired with light. I don’t think that they were going anywhere in particular, nor do I think they were eager to hunt but I am quite sure they will have a healthy brood of two, perhaps three youngsters, probably a week or two old. With a healthy and numerous population of rabbits pockmarking the fields below their eyrie, there will be no shortage of food. Their chicks, much less than expecting a feed every few minutes, will, especially at this stage, will only require food three or four times a day.
Thus, relieved of the need to sit tight on her eggs, the hen was simply joining her mate in some pleasant aerial exercise. And, whilst the survival technique of great tits and many other small birds is to produce offspring like peas in a pod, rows and rows of them, clutch after clutch, most large birds of prey produce relatively small single clutches of two or three.
But all birds of prey have devised a particular recipe for survival which sees a vast difference in size between the oldest and the youngest in a clutch. This ‘staggering’ of their young is, first of all, a result of a delay in the laying of their eggs. Secondly, it ensures that, except in the most adverse circumstances, at least the largest of the clutch will survive. In years of the shortage of natural food, the youngest – the smallest – will fail and often provide its fellow nestlings with a somewhat grisly means of survival! So nature plays the percentage game – a game which, whatever the formula, is an almost certain guarantee of survival at least for the fittest and strongest.
In most cases, come the end of the summer the youngsters will have to find their own way in the world. The parents that nurtured them so carefully throughout the summer will expel them, sometimes most forcibly, from their territory as the leaves begin to turn.
The nurturing is a long process in birds such as eagles. Their young, and often only one clutch of two will survive, do not fly until they are about three months old. Buzzards cut that time to about seven weeks.
That hen buzzard would also be free to leave her youngsters for a while because this particular eyrie is south facing and, on the day of my excursion, warmed by the heat of the June sun and protected by the cliff from the chilly northerly wind.
Mind you, with the youngsters only recently hatched, the demand for food, though constant, will be satisfied by a couple of plump young rabbits, at least for a while. However, as their young grow, those two buzzards will have to work progressively harder.
The same pattern is repeated ospreys. One good fish will keep the newly hatched youngsters going for quite a while, even though the male bird, who does most of the food fetching initially, will always take his fill of each catch before presenting it for the female to feed, first her young and then herself. However, as the summer progresses, a greater sense of urgency will build as the female will have to contribute to fetching the food. The urgency is accentuated by the knowledge that the young ospreys will have to be fit to undertake a journey to Africa in September. In a bad fishing season, some simply don’t make it.
So whilst the smaller birds busy themselves rolling clutch after clutch off the production line, birds of prey taken their time, concentrating on their one family of the year and I suspect that there will be less time available for those buzzard parents I watched, to cavort about the sky. There is a job to be done.