Sunday, 29 September 2013

Bird timetables

Red-rumped Swallow (John Hawkins)
One of the pleasures of birding, especially when visiting certain favourite places regularly throughout the year, is to mark the changes through the year with the arrival and departure dates of birds. The former are much easier to record - the first swallow or cuckoo of the spring is a simply a case of seeing (or hearing) the bird and scribbling the fact down in one's notebook (and in the old days perhaps dash off a letter to the local newspaper!), But unless one is methodically noting down every sighting of say swallows in the autumn, you are never quite sure when your last observation of the year will be until they have gone. Our family of Red-rumped Swallows are still around the garden and roosting in their nest by our kitchen door every night - but for how long? On the other hand, a friend posted a few days ago the arrival of a wintering Robin nearby, which means that any day now we should also be hearing them in the garden.

The phenology of birds' migration (i.e. the study of the timing of arrivals and departures) therefore adds a lot of spice to days in the field. At the peak of migration times, in spring and autumn, each day brings the prospect of seeing a newly arrived bird. Thus seeing the first Red-rumped Swallow of the year here may well be the highlight of day's birding in late February, whereas throughout the rest of the spring and summer, they will be familiar birds, seen every single day - with "our" nesting birds giving special joy of course. When we have moved in to a new area (it happened in Colombia, India and then Spain in 2004), one of processes of personal ornithological discovery is getting familar with the phenology, the timetable, of our local birds. Another friend here, and excellent local birder, Sergio Mayordomo has painstakingly gathered data from local bird reports over the last 15 or so years to produce a table of the arrival and departure patterns of migrant birds in Extremadura- literally a migration timetable. You can see it on this link:

http://birds-extremadura.blogspot.com.es/2013/08/phenology-of-migrant-birds-in.html

It is a great piece of work and in some ways I wish it had been around when I first came to Extremadura - but I am rather glad it wasn't - it was a source of personal fascination to navigate through phenology and discover some of these patterns myself.

There is more nowadays to this sort of study than simply marking the seasons. Phenological studies are showing us how birds are being affected by climate changes. Research has shown how Reed Warblers are now arriving in  western and central Europe 14-21 days earlier than they did 40 years ago. In southern Germany Schaefer and his team showed that the start of egg-laying moved forward by two weeks between 1973 and 2002. Earlier breeding in Reed Warblers is increasing their clutch size, their breeding success and the number of pairs that have second broods. This may be a factor to explain their increasing population. But some species which winter further south may have less flexibility because they have to finish their annual moults in southern Africa and are therefore not able to move their departure dates forward. Thus birds like Icterine Warblers are showing fairly stable arrival times in central Europe but may be suffering because the earlier springs mean that they are no longer synchronising their breeding with the peak of food availability to feed their young. In many European countries now, bird conservation bodies are taking a closer interest in pheonology of migrant birds. Like the canaries in the mines, or birds of prey hit by pesticide use, birds are proving once again their huge value as indicators of environmental health.

Sunday, 22 September 2013

Extremadura's second spring



It is a more dramatic transformation than spring itself. Whereas winter gradually turns over to spring, with a stepwise succession of flowers appearing from January through to their flourishing climax in April and with spring migrant birds too coming on board from the turn of the year,  the arrival of autumn can hit one with a jolt. And we welcome this surprise guest with open arms, a herald of the closure of the seemingly unrelentless summer heat and the start of what is really for us a second spring. The transformation happens in just days, although when it occurs is totally unpredictable. It is driven by the first rain, which can happen at any time between late August to October. It only takes a few hours of good solid rain to bring about this metamorphosis. Tiny, sharp slivers of grass shoots break through the dirt and mat of dusty, parched dead vegetation. Each one barely a couple of centimetres tall, fresh and vulnerable, but in their collective mass powerful enough to change the landscape, an alchemic conversion of dry golden pastures to an emerald sheen. Autumn flowers will follow over the next few weeks but it is the all-embracing re-emergence of grass that lifts the spirit at the back-end of the year. How quickly landscape converts to a truly lush growth will depend on the rains that follow, but the switch has now been set.

My picture at the top of the post was taken a couple of days ago, in the freshness that felt like an early autumn morning. Loose flocks of House Martins wheeled in almost chaotic fashion, before finding wires to perch on, in a tight file. Unseen against the open blue sky, a Woodlark sang gently, its cadences caressing me, whilst a Wren gave some autumn song from the brambles. The garden had other sounds too, those that I only hear at this time of year: the sharp calls of Pied Flycatchers, taking their final pause before crossing into North Africa and over the Sahara.  And crossing into view was a gliding Booted Eagle, wheeling in a low, wide circle and giving its loud, rather high-pitched "chip" calls, a vocalisation which one associates much more with their courtship in spring.

Whinchat (John Hawkins)
The autumn migration is at full pace and the plains have staggering numbers of Whinchats (photo above) and Northern Wheatears, perched on the fences, which serve as superb vantage points to spot insect prey on the ground. These alert, inquisitive birds are everywhere. Small parties of Tawny Pipits are appearing as well, sometimes perched on the wires as well, but generally preferring to be foraging on the ground.

The Equinox happens today with the sun crossing the celestial equator and autumn starts in the northern hemisphere. It was preceded by the Harvest Moon, silvering the pre-dawn sky in which hung Jupiter in its brillance. All change in the heavens indeed, but the green shoots of the year's second spring in Extremadura had signalled this all in advance.