Saturday 21 June 2014

Exciting times ahead.

I know it is mid summer and most northern hemisphere birders are not thinking yet about autumn migration but if you happen to be a male Buff-breasted Sandpiper or a female which has failed to breed, you may well already be on your way south.

Buff-breasted Sandpiper Tryngites subruficollis.

Post breeding migration for northern nesting birds is a fascinating time of year for wader enthusiasts like us, it seems that no sooner have these birds got to their breeding grounds than they are on their way back south again. Recently we have published tracking maps of Little Curlew, which show that they have only just arrived and in some cases have yet to arrive on their breeding grounds demonstrating the fact that these can be exceptionally late breeders in some cases as can both species of tattler, Lesser Yellowlegs and Long-billed Dowitcher.

Long-billed Dowitcher Limnodromus scolopaceus.

Apart from the Buff-breasted Sandpiper other species can start their southward movement in June too, Spotted Redshank and Grey (Red) Phalarope in early June with Least and Pectoral Sandpiper, Ruff and the other two phalarope species in late June. The majority of species however will be setting off during July and some won't begin until as late as August.

Spotted Redshank Tringa erythropus.

But each species does not get up as a group and migrate together en masse. Although some species may be faithful to a single partner they tend to have separate winter holidays, at least travelling at different times meaning that some birds can still be leaving the breeding grounds into September or even October.

Wilson's Phalarope Phalaropus tricolor.

In a large number of species the first birds to leave are adult females. Adult female Spotted Redshanks leave in early June and the males follow in July, both sexes of adult Great Knot and Baird's tend to all leave in July, but the females go first. In Stilt Sandpipers the adult females leave in the second week of July and the adult males a week later. In the case of the phalaropes the gap can vary, Wilson's are about two weeks apart, Red necked four weeks and Grey can be quite a big difference; adult females, once their egg laying duties are done, at the beginning of June and the adult males at the end of July.

Baird's Sandpiper Calidris bairdii.

There are some species however where the adult males leave first, Pectoral and Curlew Sandpiper and Ruff being among them.

Pectoral Sandpiper Calidris melanotos.

I have been specific above about adult males and females, this is because, and this, more than anything, is what is fascinating about these birds, the juveniles get left on the breeding grounds and then have to migrate without any guidance from their parents. It seems almost impossible that this strategy can work, but it seems to. Let's look at the Curlew Sandpiper for example, there can be as much as seven to ten weeks between the first and last birds leaving. The adult males leave in early July, three to four weeks later the females head off and then as much as four to six weeks after that the juveniles follow.

Curlew Sandpiper Calidris ferruginea.

Adults can be very faithful to migration stop over points, but the juveniles tend to migrate on a broader front. This explains why it is that many of the vagrant birds that are found around the world are juveniles and not adults. Perhaps this is a species' strategy to seek out new potential wintering grounds, but certainly once the birds start to return for their first breeding season it seems that most follow the normal patterns of migration.

Red Knot Calidris canutus.

In the case of Little Stints that turn up in the UK, it is thought that the juveniles migrate more to the west than the adults, perhaps due to the weather conditions having changed in that short space of time pushing them further west.

Little Stint Calidris minuta.

Whatever your point of view about all this, migration remains one of the greatest marvels in the world of nature, it is a strategy that has proved to be very successful for many thousands if not millions of years and yet now, it seems that mankind is determined to scupper the whole subtly balanced affair in his lust for ever greater wealth and prosperity. It is rather depressing to think that to some, these wonders of the natural world are somewhat of an inconvenience or at best an irrelevance.

Ruff Philomachus pugnax.

We hope that a general wake up call will be heard soon, and the majority rather than the minority will start to not just care, but actually do something positive to change things. 

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