Gas gun starts spring sprint

 

After a long cold late winter, spring finally arrived in a wave of migrants, with interesting reports of breeding birds now arriving thick and fast.  Spring also usually means a flurry of site visits for the Grumpy Ecologist and this year has been no different; from East Anglia to the Insh Marshes and across to Wales.   The Nene Washes are always a highlight in the spring.  Reports of a gas gun keeping Cambridgeshire residents awake at night were tracked down to an over enthusiastic booming Bittern in a fenland drain.  The breeding success of waders on the washes has been poor for the past three years, due variously to drought or flood.  Fingers are crossed for a good breeding season this year.  The cold and wet winter has left many wet grasslands in good condition; short swards with a lack of winter growth and brimming pools and ditches.

The trip to the Nene provided evidence of the seasonal changeover.  While 800 islandica Black-tailed Godwits huddled together around the pools, 30+ pairs of limosa noisily ‘wickered’ and chased around the fields.  Snipe chipped and drummed over a feeding flock of Dunlin, Ruff and Ringed Plover. Garganey zipped past the last few Whooper Swans.

Over at Ynys-hir, an early morning visit coincided with an arrival of Wood Warblers, trilling through the woodlands.  Pied Flycatchers and Redstarts were already in good numbers. All three species, typical of these West Atlantic Oakwoods, were seen well from the Ynys-hir canopy hide but the highlight was a Goshawk gliding and twisting through the still bare trees with its entourage of squawking crows marking its passage.  Wood Warblers have declined by 60% in a little over a decade (BBS data), and over a longer period have disappeared from many eastern and southern haunts, yet the reason for this decline is still unclear.  Potential causes include changes in woodland structure, increased predation and a phenological mis-match between egg hatch and the peak of caterpillar emergence. Studies in Wales have failed to point the finger at any of these and indeed have shown that the timing of Wood Warbler breeding can track the annual variation in caterpillar emergence.  Perhaps the answer lies in Africa.

The clearing infested with snakes

Grass Snake and Ramsons

With the dust barely settled after the recent house move, I’m beginning to get a feel for the new surroundings.  The feeders are out in the garden and the list is up to 40; Green Woodpeckers and Nuthatches every day are a bit of a novelty so far.  House Martins have returned to old nests under the eaves.

Just beyond the garden, Wormley Woods stretches in all directions.  ‘Wormley’ apparently is derived from the old English word meaning ‘the clearing infested with snakes’.  The ‘Woods’ themselves are considered the best UK example of Sessile Oak-Hornbeam woodland, a stand-type found on acidic, well drained soils. The ground flora of such woods is often poor, with abundant bramble, bracken and honeysuckle but little else.  However, some specialities do occur; Wild Service Tree, Great Wood-rush and Golden-scaled Male Fern.  The woods have a series of deeply cut streams running through them, many of the flatter areas swathed in Ramsons and Golden-saxifrage.  These were the woods of the Redstart, Hawfinch, Nightjar and Woodcock in Hertfordshire, now all thin on the ground or gone. The snakes are still there though.

The first trips out into the local patch have not been that exciting. Woodpeckers, Nuthatches and a few flyover Crossbills, which appear to have bred locally.  Today was a better day though; a calling Lesser Spotted Woodpecker and a fly-over Honey Buzzard.  The decline in Lesser spots has been attributed to low breeding success, with a lack of food being a possible cause.  The disappearance of one of the adults, often the female, is suggested as the cause of failure, with the remaining parent failing to bring in enough food.  Female Lesser spots have been shown to have lower survival compared to males and their disappearance may be an adaptive strategy, but it fails to work if the male cannot up the provisioning rate to match that of two birds.

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.