Friday, 18 January 2013

Totting up the Upton Birds

Nigel Robson, Volunteer Bird Recorder for NWT

NWT Upton Broad and Marshes, photo by Richard Osbourne


In support of conservation work at Upton Broad and Marshes, I have recorded birds there regularly since 2006 to ascertain their status and relative abundance. Very little has been published on the ornithology of this area.

Initially I set out to establish a status quo before major management works to improve site conditions for breeding waders and wintering waterfowl took effect. The results of this part of the study will be in my paper entitled “The Conservation Value and Population Status of Birds at Upton Broad and Marshes 2006-2011” in the forthcoming Transactions of the Norfolk & Norwich Naturalists’ Society (Vol. 45 Part 1).

The present phase of the study is monitoring changes in the birdlife after 2011. This should help determine the effects, successful or otherwise, of habitat modifications. Birds are useful indicators of environmental changes because they come and go freely, and are relatively easy to see, hear and identify. In my posts for NWT’s blog I intend to focus on this aspect, starting with setting the scene, and giving a brief resume of how bird activity in 2012 differed from the preceding years.

The reserve has two distinct but inter-related ecosystems, separated by a marsh wall (bank): undrained fen, which includes broads and carr, and drained grazing marsh. The habitat modifications affect mainly the grazing marshes. Here water levels are being raised in various sections, and areas of standing water introduced with foot drains and shallow ponds. Grazing regimes are developing to produce swards benefitting wildfowl, cranes and waders. Separately but concurrently, river defence work has created tidal lagoons, with muddy banks that are gradually vegetating to form reed swamp communities. In the undrained fen, wet woodland is being reduced to substantially increase herbaceous fen habitat, and the small (and only) reedbed is being improved for Bitterns by widening dykes within it and grading their banks to vary reed densities. The smaller of the two broads, Little Broad, has been lightly mud-pumped to partially increase its depth and release from the silt seeds of a past aquatic flora for regeneration.  



Lapwing, photo by Maurice Funnell

2012 was the first year when the habitat modifications to the grazing marshes clearly showed results. Early in the year the new areas of standing water quite soon attracted Bewick’s Swans (up to 80) and an occasional group of Pink-footed Geese including a few White-fronted Geese. Grazing duck, however, remained scarce despite a maximum of 400 Wigeon frequenting the adjacent St Benet’s Level. Winter visitors seen from time to time included a small group of Cranes and single Hen Harrier, Peregrine, Merlin and Short-eared Owl. Spring arrived as a drought-gripped eastern England, but in spite of this the grazing marshes retained some of the standing water. Consequently there was a marked increase in breeding waders: Lapwings (13 pairs) and Redshanks (4-5 pairs) doubled their number from the previous few years and Oystercatchers (3 pairs) were at their previous maximum. Single pairs of Avocet and Little Ringed Plover bred close to the river on newly created open ground, but this feature is unlikely to be retained as reed swamp takes over.

Passage waders also increased, both in numbers and variety. On the grazing marshes Whimbrel reached over 50 in April/May, some days accompanied by a few Bar-tailed Godwits and occasional Curlew (the latter occurs more frequently in autumn and winter). During the same period a few Golden Plovers (northern race) and Ruff passed through, and a pair of Black-winged Stilts even stayed for a while. But it was the riverside tidal lagoons, not yet vegetated, that attracted the greater diversity of species in both spring and autumn: Common, Green and Wood Sandpipers, Greenshanks and Spotted Redshanks, Dunlins, Curlew Sandpipers, Little Stints, Sanderlings, Ringed Plovers and a single Grey Plover.

The prolonged rainfall that followed the spring drought contributed to disappointing breeding outcomes for most of the waders. Some warblers, notably Whitethroats, Sedge Warblers and Reed Warblers, were down in numbers. Duck, however, were more successful than previously: Shelduck raised ducklings, and pairs of Gadwall, Shoveler, Teal, Tufted Duck and Pochard were present in summer and may have bred.

With rainfall consistently high throughout the first half of this winter season, the marshes are very wet. Wintering waterfowl (geese, ducks, Lapwings and Golden Plovers) have been fewer in number than during many of the winters preceding the habitat modifications. However, Bewick’s Swans have maintained a sizeable group (120+) and Cranes have been at their maximum (17). The unmodified tall hedgerows in the marshes attracted good numbers of winter thrushes early on and a few Waxwings in December. The second half of the winter may produce a different scenario!

3 comments:

  1. Upton broad is a special place really. Its a hidden treasure in Norfolk I think. A good review of it here:
    upton broad

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    1. Hi Christopher, we agree! And that is a really good review of Upton. I like that site a lot

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