Tuesday, 10 March 2015

Jigsaw spring

My first Woodchat Shrike of 2015 (Martin Kelsey)
The jigsaw puzzle that is spring is starting to take form.....every year there is the overture, embracing the exodus of Common Cranes in late February with a dramatic arrival of a first wave of summer visitors. A natural remedy: if we feel bereft at the departure of the winter soundscape of bugling cranes, so the enchantment of months' of engagement with the delightful Lesser Kestrels is gifted to us. Thus by early March, with merely a rump of a few dozen cranes remaining from the tens of thousands, Barn Swallows are already collecting mud for their nests and Short-toed Eagles hang in the sky, as if fixed for the emergence of their serpentine prey from hiberation. The gentle caressing fluty Blackbird song starts and closes the day. The pieces of the jigsaw puzzle fall, in an orderly sequence into place, species by species. The timing, phenology, of arrivals and departures fascinates all, for motives ranging from the science of evolutionary adaptation to the wider marking of the passage of seasons, with birds such as the first swallow or cuckoo being intimately entwined into our own heritage. Broadly both the sequence of arrivals and their timing are predictable, with most birds using that most constant of cues, daylength, to trigger migration. Thus, as I set out to wander in the dehesa around the Alcollarín Reservoir yesterday morning, it was a joy but not a surprise, to direct my vision towards a scratchy, almost incoherent warbling coming from the top of the holm oak nearby and seeing my first Woodchat Shrike of the year, the March sunshine making its crown appear like carefully nurtured mahogany. As it quietly chortled, two male Hoopoes incessantly bounced their "uup - uup" calls against each other, like acoustic ping-pong.

There is variation of course, brought on by prevailing weather, or the physical condition of the birds themselves. Cranes will wait for a sunny day with little wind to set off north-east out of Extremadura, anytime in the second half of February. The perturbations to normal patterns add spice to the observer of course. Over the last few days there has been an unusually large passage of Garganey through Extremadura, with drake-dominated parties of twenty or even thirty birds turning up at water bodies across the region. On a brief visit to Alcollarín three days ago, I watched 23 birds, males stiffly bobbing their heads, giving their rattling display calls as they weaved and swerved around the out-numbered females. I could have happily spent hours watching these, my favourite of all ducks.  As during my early birding years in Britain, there is an exotic ephemeral element to Garganey, wintering in tropical Africa, they make brief appearances in early spring on sometimes the most modest of pools. Two days later, just before watching the Woodchat Shrike, a careful check of the reservoir revealed just four Garganey left: three drakes and a duck.

Through natural selection, there are changes happening with migration timing and direction. With climate change and the shifting forward of annual cycles of many plants and insects, there can be a selective advantage on those birds which migrate earlier, to keep up as it were with the supply of resources on which they depend. As well as individual differences, there are differences too between species on how flexible or adaptable they can be. Reed Warblers are now returning to breeding grounds in Europe 14-21 days earlier than they did 40 years ago, whereas Great Reed Warblers with their longer migration routes are only arriving a few days earlier than before.

Great White Egrets (Martin Kelsey)
I paused and watched a line of Great White Egrets on a weir. Another example of change, I reflected. Formally a great rarity here in Spain and across Western Europe, its spread from the east has been exponential. One of the birds (the right-hand bird in the picture) was colour-ringed, probably (but this will be confirmed) in France. Through the traditional ringing but especially now with satellite-tracking and other technology, we are slowly starting to visualise better the movements of birds, not just the starting points and their destinations, but most intriguingly what they are doing on their travels as well.


1 comment:

samuel langlois lopez said...

Another fine, expertly sculptured portrait of your local patch. Great pleasure to read as always.

Abrazos

Sam & Dave