Many people are attracted to the first migrants of the summer and welcome back the cuckoo or the willow warbler let alone the swallow and osprey. These are summarised in the annual reports of the Highland Bird Report where there is always a page that covers the first dates back for such migrants. There is a sprinkling of birds in March each year such as the osprey, ring ouzel and wheatear followed by a number of birds in April such as cuckoo, chiffchaff and redstart. Some birds delay their arrival in the Highlands until May such as the swift, garden warbler and spotted flycatcher. Each year I try to match these dates with my own observations but my dates are always much later than the ones given in the Report. This is despite the fact that I often make early visits to suitable places such as the coast, woodland, moorland and lochs.
This year I have made a point of looking at the last dates in the report for migrants rather than the first, and, particularly, looking for swifts, sand martins, house martins and swallows. The swift is the odd one out because the adults will leave early. The last dates for swifts to leave for Africa is around 5th September and they leave fledged chicks behind that are independent as soon as they leave the nest and make their own way to Africa. What is remarkable is that the young swifts I saw leave early in September will not land again until they are looking for nest sites 23 or more months later. They eat, drink and sleep on the wing.
The swallows arrive around 12th April in the Highlands and if it is a good year for insects they can have two broods even this far north. The photograph shows what is almost certainly a second brood although this year, with the insects so low in numbers, it was the exception. In some years in the Highlands the last dates for swallows are into November. It makes one wonder whether, in the future, some swallows will over winter up here as each year there are scattered records down in southern England for the whole of the winter. Swallows and sand martins will often flock up just before they migrate south and in reed beds huge numbers may gather to roost overnight.
Sand martins leave around 12th September after joining the swallows in their communal roost that may number in their hundreds. They have an annual threat to their choice of breeding sites as they nest in colonies in the sandy banks of rivers and wide burns. The problem is when the rivers and burns experience a spate if the water rises too quickly over too short a time. The time of such spates is critical as if the young sand martins are still in their breeding holes and cannot fly they may well be drowned or just washed out when the water rise above the colony of holes. There seems to be a trend for sand martins to change to colonies away from the water although still within a short flying distance of water where their main food, insects, will gather in high numbers. I now know of at least three colonies in such a situation. Fortunately this year the spates after heavy rain did not materialise and the large colony below our house went unscathed and had a good breeding season. They will now be well on their way to Africa.