Nature never stands still. As the year ticks along, changes are always in the air. Sometimes the changes are subtle and thus hardly noticeable. At other times, when seasons change for instance, they are more radical and thus easier to see and appreciate. Right now there is change which is more obvious to the ear than the eye. Furthermore, this is a subtle change, for we have now entered the season of silence!
Now, it is indeed the sound of silence that suddenly descends on our landscape, as most birds cease to exercise their vocal chords. You may well ask, "Where are all the birds?" After what has seemed to me to be an especially tuneful year, with in my estimation at least, many more migratory birds present than usual, there is now a deafening silence. A week or ten days or so ago, I heard a couple of quite muted whispers of willow warbler music. It was as if these two individuals at least, were having a rather half-hearted vocal fling, before submitting to the truth that they have entered the moult and that for the time being, it is not a good idea to advertise one's presence!
For most birds, the breeding season is now over, so the next phase in their lives is to begin their annual moult, a process which for most, occurs during July and August. And in the case of those that are migratory birds, one factor is key. It is vital that by the time they are impelled to answer the call of instinct and begin to prepare for their forthcoming epic journeys, their new sets of feathers are in first-class condition. Hence, the process of moulting and replacing feathers is completed in double quick time, in some cases in no more than three weeks, for those birds destined in September and October, to head off for a winter in the Dark Continent.
Of course, there are exceptions to the rule. If there has been generally a very noticeable muffling of song, the bubbling twittering of two male swallows in recent days, sounding especially loud against that background of silence, indicates that they at least are not yet done with their breeding season. For them and indeed for the house martins seen and very much heard on a visit to a friend's house, there is still work to be done. With a third brood of youngsters recently hatched, the martins' summer is far from over. Thus the otherwise still air was filled with their celebratory and delicious mellow twittering.
There has also been in recent days a rather less melodious sound here, emanating from this year's crop of young magpies. Theirs is a difficult sound to describe. A cackling screeching probably comes nearest! Meanwhile, there are other birds with work to do such as the local ospreys, now feeding youngsters, which will probably not leave the eyries that have been their nurseries, for a few weeks yet. Soon however, they will be climbing out of the depths to perch on the edge where they will begin to exercise their wings in preparation for their very first experience of flight at seven or eight weeks old.
From then on those chicks will be in the race of their lives, with time their greatest enemy. One day towards the end of next month, the parents that have so carefully nurtured them, will up sticks and go, abruptly starting their journey to Africa without so much as a 'by your leave' or even a 'good-bye'! It is therefore imperative that those youngsters will have to become self sufficient enough to catch their own food before they too must answer the call of navigational instinct and depart on an epic journey of three thousand miles or so. When they also finally leave, theirs will truly be a flight into the unknown! If they have not learned well the techniques of catching fish, their migratory journeys are bound to end in disaster.
For much of her time here, the female osprey is quite sedentary. She undertakes most of the incubation duties, a process that lasts some thirty-five days or so. She undertakes most of the incubation duties, a process that lasts some thirty-five days or so. She too takes on much of the responsibility for brooding her youngsters and so during that long spell of enforced idleness she sensibly undergoes the moult. Her mate however, with a summer-long responsibility for obtaining food for both his mate and his progeny, waits until he is back in Africa before he goes through the process.
In general, however, there is a distinct difference between the rate of feather shedding and renewal for sedentary birds as compared with those that spend their winters overseas. As said, migratory birds need to complete the process quickly in order to be in the best possible condition for their long journeys. In contrast, bullfinches, which remain here throughout the year, take their time, beginning to shed feathers during these July days but not acquiring an entirely new set until late October. Ravens however, take even longer, beginning their moult early in the year during the breeding season and not completing it until around 150 days later! Female sparrowhawks and peregrine falcons also go through the moult during the breeding season.
For migratory birds, as the process clearly has to be completed in time for them to set out on their journeys, means that the rapid loss of feathers badly affects their capability to fly. Thus, they tend to skulk and stay well hidden. It follows, that for much the same reason they also choose to stop vocalising. So they are accordingly harder to see while obviously it is also impossible to identify them from their songs, as they fall silent! Their main aim is to remain well concealed at a time when they are particularly vulnerable to attack by predators, especially at this time of the year. Now of course, there are even more raptors to contend with, in the shape of newly fledging generations of hawks and falcons!
However, several of the more sedentary birds also take their time to complete the process. Many of our waterfowl are so debilitated that they cannot fly at all during parts of their moult. They mostly take refuge in places such as marshes but others undertake short migratory journeys. For instance, many shelduck resident in Scotland gather in their thousands off the Aberdeenshire coast. Large numbers of Canada geese, now so much of a presence across the UK, travel to the Beauly Firth to moult.
One of the birds, which during this summer, as I've often said, has been heard in just about every airt, seems however, to buck the trend by undergoing two moults each year. Willow warblers, whose voices seemed to provide me with a prelude to the 'season of silence', like many of their warbler cousins and many other migratory birds, undergo a moult here once their breeding season has been completed. But they also go through another moult during the winter months once they have reached their winter quarters. Furthermore that moult seems to last a long time, continuing almost until they are ready to begin their return back to the lands of their birth.
It is presumed that they undergo these two moults because they tend to dwell in thick undergrowth and therefore need to renew 'tatty' plumage more urgently than most. Yet there are plenty of other birds, which spend their lives in similar conditions. And they moult just once a year. So it might just be the case that willow warblers have taken the process to a different level?
And then, just as I was beginning to think that silence was, after all, golden, up piped the most vociferous of them all ... jenny wren. The vow of silence taken by most of the avian classes was soon broken again, this time by a tuneful goldfinch. A snatched moment of pure gold to break the silence!