Wednesday, 28 March 2012

Glossy Ibis mystery solved

'Er indoors said she fancied some tapas.  Eager to please as always, a weekend trip to Seville was swiftly organised.   Seville has 300 or more tapas bars, but we didn't manage them all.  We made a start at El Rinconcillo, with a glass of fino and a plate of acorn-fed, luscious, red, iberico ham.  On to La Giganta for a salmorejo of orange and salt cod and some slow-cooked pigs cheek, with a glass of fino or two. Then to the tiny 'one man and his gas ring' Bar Eme for a wonderful plate of coquinas washed down with fino.  And so on.  You probably get the idea.

After many a clam was dispatched, dripping in olive oil and garlic, we moved on to Donana.  Overnight rain and southerly winds had left the bushes dripping in migrants.  Willow Warblers, Whitethroats, Redstarts, Subalpine warblers, Wheatears, Woodchat Shrikes and Nightingales were everywhere.  We set off at dawn with our guide, firstly exploring the Stone Pine and Cork Oak forest. Serins sung from every corner; Woodlark, Crested Tit and Azure-winged Magpie were added along the way.  Mammals were the key target at this time though and an essential first stop was a regular watering hole for an Iberian Lynx.  Further down the track, half a dozen Wild Boar scuttled away.  Lynx have increased in recent years, with around 80 animals now present in the national park.

Once out onto the marshes if was clear that Donana was suffering from a major drought this winter.  There were far fewer birds than normal.  The expanding population of Glossy Ibis, now 1,000+ pairs, is expected to have a poor breeding season this year, with many birds having departed to the north to seek more favourable conditions.   Hence the remarkable numbers in the UK this winter. The remaining pools held a few Ibis, Teal, Garganey and Shoveler.  The reed edge revealed 2 Spotted Crakes, 2 Purple Herons, Little Bittern and Great Bittern.  Isolated bushes all held migrants; best of all, a Ring Ouzel and a splendid male Black-eared Wheatear.  The dried-out wetlands had a column of Griffon Vultures descending to a dead horse and singing Calandra Larks were everywhere.  As the sun rose high into the sky, a spot of raptor watching added Spanish Imperial, Short-toed and Booted Eagles, and Lesser and Common Kestrels to the vultures and ubiquitous Black Kites.

Finally, to the main flood by the town of El Rocio.  Hundreds of Flamingo, Shoveler, Teal, Black-tailed Godwits and Coots worked their way around the shallow, drying lagoon.   Our guide had said check every coot carefully, a technique that finally ‘dug out’ at least 4 knob-less Red-knobbed Coots from amongst their even-more knob-less cousins.  Northward-bound waders fed furiously around the margins, with half a dozen Temminck's Stints being the cream of the crop.  Streams of birds circling down from on-high signalled the first major arrival in the area of Collared Pratincoles and Gull-billed Terns.

It was time for more fino and coquinas before contemplating the agonies of the return flight with Ryanair, the company that puts the customer last.  Pallid Swifts screamed their approval as we snuck a few extra pounds past the hand luggage Gestapo.

Below - Sharp-ribbed Salamander, Jamon Iberico and Black-eared Wheatear.

Thursday, 22 March 2012


Or does it?  Usually a sound equation for breeding Bitterns is good supply of fish, especially Eels, added to a wet reedbed.  As the Bittern booming season gets going, with the remarkable early news of up to 30 boomers in Somerset, a very few sites stand out as being stuck in the recession.  The most noteworthy is the former Bittern stronghold of Leighton Moss, where I recently returned to undertake two days of electro-fishing and take a long, hard look at the reedbed.  The major concern is the almost terminal decline in Bittern, against the national trend.

Leighton Moss supports one of the best densities of Eels and other fish that we have come across, yet the Bitterns are declining.  Recession is indeed the problem; recession of the reed margins that is, making the fish less available to a foraging bird. The problem of reed recession in old reedbeds is well known.  The formation of toxic by-products by the reed litter under anoxic conditions in high, stable water conditions reduces reed shoot density and vigour.   Reed re-colonisation into anoxic sediments is known to be poor. 

However, when reedbeds cease expanding (or start dying-back) due to the ageing processes described above, or grazing (by geese or deer for example), their extent can be increased by lowering water levels to expose mud and allow new plants to germinate and establish.  Periodic drying out can be used to increase or decrease the proportions of open water and swamp vegetation and effectively rejuvenate the habitat.

Such a pattern of management has been used in the Oostvaarderplassen in The Netherlands.  A mosaic of reed and open water habitat is maintained by a combination of fluctuating water levels and grazing by moulting Greylag Geese. This results in a periodic expansion and regression of reed.  During high water levels, the geese graze back the margins of the reedbed.  During low water levels, the exposed mud is colonised by reed, other swamp plants and ruderals.  When water levels rise again, the seeds of the ruderals provide food for wildfowl and the new reed shoots form an expanding reedbed.

However, such management may seem drastic, particularly when short-term views are taken.  But, in a recession, do you simply squeeze tighter and deliver the Bittern’s P45, or try to promote new growth?

Thursday, 8 March 2012

Woodlands - the forgotten wetlands

A walk around my local Broxbourne Woods was rewarded with a now irregular sighting of a Hawfinch, once a frequent bird in these parts. There has been a steep decline in many woodland birds over recent years – Lesser Spotted Woodpecker, Willow Tit and Hawfinch all come to mind. However, this decline is not ‘across the board', with some of the more generalist species doing well. Some of the declines have been linked to changes in woodland structure, but in the case of the Hawfinch, the reasons for the decline are still unclear. There has been a 78% decline in the breeding distribution of the Hawfinch between 1970 and 2010 (although there have been some gains in winter distribution). A large number of hypotheses have been put forward to explain this decline, and they include the impact of increasing deer populations, woodland management practices, and of course, the impact of predators.   Hawfinches are mainly associated with extensive areas of mixed broad-leaved woodland, with mature trees, and with an open understorey. There are hints that they prefer woodlands with wet features and that they have disappeared from sites with high densities of Grey Squirrels. Jays are also suspected to be a major nest predator yet evidence remains anecdotal.

The link with wet features is interesting as the importance of wetness in woodlands is surely undervalued. Visit many woodlands and you will see a network of ditches alongside the rides. Many of these were put in to drain water off the site and allow easier removal of timber. Take Wolves Wood in Essex as an example. The ‘old boys’ will tell you that visiting in spring was a nightmare; flooded paths and mosquitoes everywhere. Well, times have changed. Everywhere is drier, yet many of these woodland ditches still drain away winter rainfall. Flooded paths and mosquitoes are a thing of the past. With many woodland birds declining, the loss of Nightingales, Song Thrush and Willow Warblers from some areas could well be the result of reduced invertebrate food as a result of drier conditions. At Wolves Wood, recent work has been undertaken to block up all the ditches as they leave the woodland and extra internal bunds have been constructed to hold water back in the ditches and ponds. The aim is to try and retain winter rainfall and make the site wetter again. We wait to see if the birds and mosquitoes respond.