Sunday, 20 February 2011
Friday, 18 February 2011
Brents at Old Hall - keep eating chaps. Spot the Brant.
The ‘improved’ grass fields at Old Hall Marshes are managed to provide winter grazing for the internationally important numbers of Dark-bellied Brent Geese in the Blackwater Estuary. The fields are prepared to provide the lush sward of fine grasses the birds prefer to eat, with a target grass height of 50-100mm in October. The ‘by-product’ of a winter's grazing by geese and Wigeon is a tight, occasionally tussocky, short spring grassland that attracts nesting Lapwings. However, in recent years, Brent numbers locally have followed the national trend of decline. There has been less grazing in the fields, resulting in a spring grass height somewhat longer and poorer for Lapwings.
Today the sward measuring boots had an outing to the various fields at Old Hall. With reduced grazing and warmer winters, additional grazing may now be required to bring the spring sward into an ideal condition. Formerly fertilised, farm-yard manure is now added to the fields; the Dutch traditionally do this in late winter to bring earthworms towards the surface for the benefit of breeding waders such as Black-tailed Godwits.
Around 3,500 Brents have been using Old Hall of late, with around 18% of young birds suggesting a good breeding season in 2010. The flocks of Dark-bellied Brent today also harboured a Black Brant and a Pale-bellied Brent. Six white-fronted Geese were nearby. Displaying Marsh Harriers were continually in the air (up to 10 birds together), and Merlin, Peregrine, a couple of Ruff, Pintail, Scaup, Bearded Tit and a few of the recently recorded 1,800 Grey Plovers were amongst the mass of birds on offer today.
Saturday, 12 February 2011
The William Girling - a bit like the sea but without sand, or salt, or sun, or birds (except B-n G's).
The William Girling Reservoir holds the largest wintering group of Black-necked Grebes in the UK. Yet this is not a bird-rich site. It is not especially favoured by diving duck, it is shunned by Shoveler, poo-pooed by Pochard and used principally as a dormitory by dabblers. It is a concrete doughnut holding water. But presumably the B-n G’s have some competitive edge here. Although there are occasional records from other sites in the Lee Valley, no other local site regularly holds wintering birds. The peak count on the Girling over the last ten years was of 32 birds in December 2007. Peak winter numbers have been around the mid-20s for the last three winters.
With 24 birds arriving on the reservoir in the first week of August last year, around this number of birds have remained all winter. Numbers are just beginning to drop as the first birds move off, 18 were still present today. Seven months on the Girling! What is there left to eat?
Black-necked Grebes are a specialised invertebrate feeder, principally seeking aquatic insects and their larvae by ‘gleaning’, although they may also take molluscs, crustaceans and small fish. They tend to favour shallower waters in the summer, moving to deeper, mainly coastal sites in winter. This concrete-edged basin with water depth of around 14 metres would seem to be at their edge of tolerance, with BWP stating diving depths of up to 5.5 metres for up to 50 seconds. Birds diving around the margins (where there are concrete ‘roads’ a metre or so down) stay under for 30-40 seconds, whilst those well away from the reservoir margins re-surfaced after 50-60 seconds. It would be fascinating to find out what they are feeding on. The other big question is where are they between February and August?
Tuesday, 8 February 2011
Spring seemed just around the corner today, with glorious sunshine at last and reports of booming Bitterns coming in from the south-west. So, with a trip down to Rainham Marshes, thoughts turned to maintaining ideal water levels through the coming breeding season.
A lot of work is happening at Rainham this winter, not least a review of the hydrology. Maintaining adequate water into the summer is a key issue; essential for providing good feeding conditions for breeding and passage birds. Good work by the site staff over the winter has blocked some of the seepage points identified last autumn. The Target Pools look particularly good at the moment, with higher than usual water levels – but the test will come in the spring as water levels naturally drop. The overall aim should be to achieve a strategic approach to water level management, a succession of good feeding areas around the reserve through the year. Various trials involving moving water around the site should indicate if this is possible.
Yesterday's Penduline Tits failed to re-appear, but with good water levels the reserve was holding large numbers of birds, notably Lapwings, Wigeon and Teal, and of course gulls. Meanwhile, back on the garden feeders, Mealies continue to feature; up to six amongst the 20+ redpolls.