Wednesday, October 27, 2010

Changing behaviour of the White Stork

The site of a mass of White Storks migrating across the Strait of Gibraltar is still a typical sight in July, August and again between November and April.
These are largely Iberian breeding birds which arrive and go with the rains. Their spring usually starts, variably in October, November or December, depending on when the rains come.

Choice of breeding habitat varies. In south-western Iberia many nest in trees (below) and feed in the rich marshes (above), on frogs, crustaceans and fish. 
Adult peers from nest in eucalypt (above) and two chicks sleep in their tree-top nest (below).

Here they often nest in large colonies alongside Grey Herons and Spoonbills (above) but they may also nest alone (below).

In western Iberia they often feed on the open plains (above). In the absence of trees they often make their nests high in the rooftops of medieval towns (below).

In spring they make the most of the wet and grassy fields in the oak dehesas where they take a variety of prey. Come the summer, when the fields dry up, they exploit the abundance of large insects ahead of the migration south (below).

Bush Crickets (above) and grasshoppers (below) are favourite prey in the early summer.

Traditionally, these storks left with the summer drought to spend the months of July to September in West Africa, south of the Sahara. Here, in places like the wetlands of the Niger in Mali, they would arrive precisely with the monsoon rains. With the end of the rains in October they would start returning north to catch the start of the rains north of the Sahara Desert.
...but for a few years now this pattern has started to change with many storks never leaving at all.
They have the advantage that, being on or close to the breeding grounds, they can time the start of nesting much better than their counterparts in Africa.
so what has changed?
we changed! We developed the habit of creating large, open air, rubbish tips and the adaptable storks learnt to scavenge here during the breeding season. Food was easy to get and, as the supply did not vary with the season, they never left.
so storks now patiently line up and wait for the next refuse lorry which brings many potential meals!

so we can imagine a time when we produce so much refuse and have so many such tips, that the entire pattern of the storks' behaviour will have changed from migratory to resident.

Monday, October 25, 2010

Magic of La Janda - the Black-winged Kite

The Black-winged Kite inhabits open areas with scattered trees in western and southern Iberia. It is a species that also breeds in Morocco and which finds in Iberia the northern edge of its range.
This beautiful bird seems to have experienced a range expansion during the twentieth century and its success has been linked to the spread of managed dehesas - open parkland with grazing mammals - which is structurally similar to its native African savannahs. It is here that it finds the small mammals which make up a large part of its diet.
La Janda, former site of Spain's largest lake, in south-western Spain is a favourite site of these birds in the autumn and winter. Here the habitat is ideal for this species that arrives in substantial numbers making La Janda a great place to see these birds.
La Janda showing typical Black-winged Kite habitat. Riverside poplars surrounded by fields with the town of Vejer in the background (above) and olive dehesas in spring (below).

During migration time this habitat is also used by passage Black Kites (above), here waiting for the sun to clear the morning mist. Marsh Harriers (below) also frequent the canal embankments where the kites also hunt.
The greatest competitors seem to be Kestrels with which they often fight (below).
This competition seems to be for prized perches from which they patiently watch for prey on the ground (below).
This leads to spectacular interactions between different kites (below).

But they also hunt from the air with their unique yawing glide, with wings held up. Their black upper-wing is then most obvious.

The juvenile birds of the year (above and below), with traces of brown plumage and a scaly upper wing pattern, seem to stay close to the adults in the autumn but they hunt independently.

Watching these birds is one of those priveleges of Nature that are hard to describe. I hope these photos have gone some way.

Thursday, October 21, 2010

Wintering passerines arriving each day

Most of the trans-Saharan migrants have gone through by now and it is the turn of those that will spend the winter in our area. Among these are the Chiffchaffs from north-western Europe.
These small insectivorous birds are great opportunists, a good quality if you are a migrant. At this stage they spend their time in marginal habitats where flowering plants, like the Aromatic Inula (above) or the Culinary Fennel (below), attract many insects.

Blackcaps (above), distinguishable by their pale plumage and long wings compared to the local birds (see post of 12th March), and White Wagtails (below) are among the most numerous of these arrivals.
Now commencing is the spectacular diurnal migration of finches which will dominate the scene in late October and early November when the skies get covered in flocks of Chaffinch, Greenfinch, Serin, Linnet and Goldfinch (below) in particular.

Wednesday, October 20, 2010

Return of the Gannet

Gannets return to the Strait of Gibraltar during September and October. Juvenile birds are most obvious at first and are the ones which migrate furthest, reaching down to tropical West Africa.
These birds were born this summer in colonies on the north-west coasts of Europe, in France, the British Isles and Scandinavia and quickly make their way south to avoid the harsh northern winters and make the most of the concentrations of fish in the Strait of Gibraltar and coastal upwellings along the proximal Atlantic coasts of Portugal, Spain and Morocco.
Large shoal of Grey Mullet off Gibraltar today (above).
These birds will now remain with us until the spring and many will linger on through their first summer. It is only as they get older, and their plumage progressively whiter (below) that the urge to migrate north in the spring gets stronger.
So here are a few more images of these amazingly "painted" birds, which appear drab and brown at distance but which reveal beauty at close quarters - don't you think so too?