August 2nd   Leave a comment

This morning was practically windless. The sea flat half-way out to the May: if there had been any dolphins about they would have stood out a mile. I did an optimistic circuit of Balcomie and Kilminning without any real expectation of finding anything, but found that everything was worth seeing. Even a chaffinch seems worth seeing after a month without them. I noticed a lot of young birds. At this time of year you can begin to get an idea of how well the breeding season has gone by counting the number of adults relative to the number of juveniles. Goldfinches are perfect for this. The young lack the head pattern of the adults and so look strangely bald. It is easy to count them as they perch in a line on a telephone wire. For example in one group I counted 7 young and 2 adults – so 3.5 per adult, or 7 for a pair. Not too bad when you realise that each adult needs to produce one young in its life to replace itself and so have a stable population. It is a bit more complicated than that because you need to factor in how long the adult might live and how many young ones will die before they get to breed themselves next year. If, for example, we assume realistically that half the adults die over the winter and three quarters of the juveniles (youngsters always have a much higher chance of dying in their first year as they try to find their way in the world) then we would be left with one adult and 1-2 juveniles by the start of next summer. A positive balance sheet but fairly tenuously so. If in a bad summer each pair only produced 3 young then this would shift to a decline in the population for that year. Good years can make up for bad years of course, and vice versa. It takes a lot of information to work out therefore if this year is good or bad for breeding for any bird, but on first sight it looks like the goldfinches have done well. Same with the swallows I think, also the buzzards and kestrels I saw today (you can tell the adults in birds of prey at this time of year often because they are missing flight feathers as they moult: the young have just grown a nice new set so have perfect-looking wings). For some birds the adults and juveniles segregate after breeding so this simple counting doesn’t work. The black-headed gulls roosting on the low tide shore off Crail today were almost entirely adults with may be a couple of first years for every 25 adults. The youngsters are mostly still inland, where they were born, and will work their way to the coast over the next month or two.

Juvenile black-headed gull - ready for its future life of crime?

Juvenile black-headed gull – ready for its future life of crime?

It’s young herring gull time again around Crail. The surviving chicks are now large and able to fly but still hang around the rooftops where they were born mewing pathetically. I notice that they (well at least “seagulls” – which is like referring to problems in Africa, yes, but which country do you mean?) have become demonised again in the last month. Yes, some gull species do well in the chaos we have created with our superabundance of litter to feed on, removal of the larger predators and changes of habitat to suit them. But in a world with a higher priority in maintaining “natural” habitats and ecological communities we would not have such a problem with gulls, or the next “pest” species that we will inevitably create.

Posted August 2, 2015 by wildcrail in Sightings

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