Sunday, 10 June 2012

Avocets, Little Terns and more...

We’ve spent most of the past week fairly close to Tavira.  Otherwise, there’s been just one trip to Castro Marim, a walk around the water treatment ponds (ETAR) near Faro on a day when we had to go to the airport and a morning spent checking out a couple of White-rumped Swift nest sites inland.

Locally, we’ve been taking a particular interest in the nesting Avocets.  There must be close to 100 pairs on the Tavira/Santa Luzia saltpans and this week has seen the hatching of the first of the year’s young ones.
Unfortunately, last weekend some nests were lost when they were flooded by a slight rise in the water level in one of the pans.  It was only slight but combined with a strong wind it was enough to put paid to about a dozen out of the 40 nests that were strung out along a bund across the middle of the pan.  A pair of Little Terns also lost their eggs.  Thankfully, the level has since dropped and the remaining nests now look safe enough.  We were worried about the nests on another pan when we saw water being pumped into it but it does look as though most of those will be OK.

Other Avocets have chosen safer sites and no doubt the next few days will see lots more chicks emerge.  That will also result in an increase in the decibel level as the adult Avocets noisily chase off intruders, particularly the Yellow-legged Gulls.  They have been biding their time these last few weeks, preferring to wait for chicks to eat rather than settle for eggs!

Also nesting around the saltpans are Black-winged Stilts, Kentish Plovers and just a few pairs of Common Redshanks.  Not nesting are the Dunlins, Sanderlings, Grey Plovers, Oystercatchers, Curlews, Whimbrels, Black-tailed & Bar-tailed Godwits and Ruddy Turnstones that are still here.  Although many of these birds have moulted into something approaching breeding plumage, we have to assume that at this late stage they’re not intending to migrate north to breed.  No doubt, most are birds in only their second calendar year.  Next year they will have reached full maturity and be ready to find a mate but right now they seem happy enough in the Ria Formosa.  Some, on the other hand, might for some reason simply not be fit enough to moult or migrate.  Maybe they’ve worn themselves out getting here from somewhere much further south.

This morning we came across a disused saltpan that was alive with small black flies, a food source that was being exploited by a group of about 20 Little Terns.  It appeared that as the terns swooped down and skimmed the water surface, the flies would take off and immediately find themselves gobbled up just an inch or so above the water.  It’s a very different feeding technique from the one we’re used to watching Little Terns employ when their diet is mainly small fish.

Not surprisingly, a Yellow Wagtail had a different approach to catching the same flies.  In a corner of the pan there were hundreds of flies settling on some floating weed.  The wagtail simply dashed around after them on foot and seemed to be having a fair amount of success.

White-rumped Swifts are still quite scarce birds in Portugal – we know of only six sites where they have bred.  At the end of May we found one of these sites in the Alentejo to be occupied again this year; a Red-rumped Swallows’ nest had been decorated with a feather in the entrance in the way that White-rumped Swifts do when they take them over and we saw a White-rumped Swift approach the nest.  Yesterday, we were disappointed that the two sites in the Algarve that we checked showed no sign of White-rumped Swifts being in residence.  At the one site there weren’t even any Red-rumped Swallows; at the other there was at least one active Red-rumpeds’ nest, so maybe there’s still time for some swifts to move in and use it.

Our recent comments about the increase in the number of Black Vultures proved to be prophetic as we saw one yesterday in the Algarve, quite an unusual occurrence at this time of year in our experience.  It had wandered quite a way south from where we normally expect to see them and was only about 25 kilometres from the coast as the vulture flies.

Our walk at the ETAR was notable for the number of young Common Shelducks.  There was a brood of 12 quite well-grown ones and then a crèche containing 48 very young ones of about the same age but presumably belonging to four or more pairs.  Where do our Shelducks go to moult, we asked ourselves without finding an answer!

Also at the ETAR were three Glossy Ibises and a single Sacred Ibis and at a nearby fish farm an Osprey seems to have settled for spending the summer on its own without the complications that come with having a mate and a family.

Highlights at Castro Marim were about 50 Slender-billed Gulls, two Black Terns and at least a couple of Collared Praticoles.

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