Saturday, 23 April 2011

Easter week-end

This spring continues to leap ahead of all expectations, except perhaps rainfall, which has been zero.

A benefit of producing blogs and newsletters is that you can look back on the same month in previous years. I've been through my photo albums too, and most of what I'm photographing now is usually stored in my shiny Mac computer under May!

Although some migrant birds are still arriving, most of the ones that will stop to breed with us seem to be here already. This week we have have added whitethroats and garden warblers to our list of breeding birds while black terns and wheatears have passed through.

If you overlook the Heronry Lakes on most days, you can witness a remarkable aerial ballet as the black-headed gulls and common terns that nest on the Sailing Lake feed low over the water. They are not fishing, but gracefully, almost casually, hawking for insects, just like swallows.

There are massive swarms of non-biting buzzer midges (Chyronomus plumosus) and caddis flies (Trichoptera) that hatch from the lakes and then make for the surrounding trees. When they first emerge, these insects are very vulnerable as they are weak fliers. Look for swarms of the midges in columns over bushes or fence posts. They look like smoke from a distance.

If you watch these swarms closely, you will see that they are composed of females. The larger males, with feathery antennae, come in to grab a mate every now and then. Of course the swarms attract predators too. Look for black St Mark's flies (Bibio spp) which have a pair of long dangly legs, used for carrying off midges for dinner. They always emerge when the May blossom is out, or at least on the Saint's day, but they were a week early this year. St Mark's Day is April 25th.

If you are keen on insects, then this is an ideal time to get out and look because there is something new every day. This Emperor Moth was seen in a Little Paxton garden this week. I see one most years at this time. Last year there was one in the little orchard by our tractor-yard. They are day-flying silk moths, and every bit as spectacular as the photo of a female suggests. It's hard to get a picture though because they hardly ever seem to land once they have warmed up enough to get going. I'm always amazed to see them as they should be on some heathery moor, miles from here.

Anyway, back to the gulls and terns on the Heronry Lakes! They can survive quite well on flies but the problems start when the chicks start to grow in the nest. They need something bigger with more calories per serving, such as fish fry. At the moment the fry are as tiny as insects. Anglers call them pin-fry. But as the chicks grow, so do the fry so that by June most of the small fish will be inches, not millimetres long. You will soon see the terns carrying fry to their chosen partner in courtship, then later to the fat chicks on the islands in the Sailing Lake.