Over the last couple of years I've been regularly taking the opportunity to look at the Curlews (and other species too) feeding along the Upper Humber, study, photograph and video them and look at what habitat they are preferring to use. Part of this was originally to look at how we used our grazing animals here at Blacktoft to ensure we maintained feeding habitat for what is currently one of Europe's fastest declining species.
Is mixed grazing improving the habitat on the reserve for curlew?
You see when I first started on the Humber just over 20 years ago the status of curlew was very different at Blacktoft, during the late summer we had several hundred birds flying west as they came in from Europe heading for places like Morcambe bay where up to 18,000 wintered. But few birds fed on the the reserve apart from out on the mudflats where the confluence of the river Trent and Ouse join to form the Humber Estuary. Several hundred birds did winter nearby around Whitton Island and Broomfleet but they declined and it was never fully documented as to why and at the time few moved up the estuary onto the reserve to feed.
This was often the view you got of curlew as they headed west!
But now we don't seem to get the same number of birds heading west and this is maybe confirmed by the declines recorded at places like Morcambe where they only record about 12,000 birds each winter. However, the reserve seems to have had a change in fortune with birds now wintering and feeding on both the tidal mudflat and also our Konik pony, cattle and sheep grazed Ousefleet foreshore for most of the winter. This year has in fact seen 118 birds gathering in front of the hide and often good numbers feeding on the grassland. I also suspect that with the creation of Alkborough and introduction of more grazing wintering curlew number in the Upper estuary have had a revival in fortunes with I suspect over 700+ wintering this side of the Humber bridge which strangely goes against the undoubted catastrophic international population decline of nearly 50%.
Here's a bit of video of one of the birds feeding on the Konik grazed area that has then been flailed
Initially I wanted to look at what had caused this change but more recently as I've learnt a bit more my attention has changed towards a more landscape view and how does this translate to curlew along the whole estuary? One thing is clear is that food resource on the estuary declines as you head west as salinity decreases and species like lugworm decline, I certainly know you get them at Reads Island in low density but when you get to Blacktoft they are certainly getting pretty rare.
Part of a flock of 700 curlew at Reads Island late July/August, numbers often build up here at this time with many birds eventually heading west?
Recent observations particularly over this winter have started to shed a little light upon this and certainly suggested that it is very much to do with organic content of the top 1ft of soil that increases the number of prey items particularly worms, beetle larvae, and leather-jackets (crane fly grubs) although some photo's have also revealed that curlew are also taking grain seeds too within stubble. So here's a quick summary of the areas where curlew like to feed and why
You can clearly see here that this bird is feeding on the smaller species of worm that feeds on dung and vegetation
Curlew feeding - soft soil is good for worm extraction!
Its been fairly well documented that many modern arable fields lack organic material as farmers have moved over to artificial fertilizer rather than organic manure and that these fields often hold low densities of earth worm. Its also interesting though that some farmers who I work with are now looking at how they get more organic into their soils, so this certainly is a great positive change if into the future it can provide more food for the Humbers curlew, golden plover and lapwings!
The main feeding habitats of the Upper Humber from observation
Mudflat
Curlew in long stubble near to Whitton - they seem to particularly like it about 20cm long or belly height!
Short sheep grazed grass, this field was only seeded a few years ago at Alkborough top and seems to be particularly productive
Mown riverbank - some of the sections that are just mown seem favoured feeding at times
Longer but grazed grassland, the grass here is short turf in with the long turf even though the curlew are almost hidden
Shorter mixed grazed grassland
Arable fields that I suspect have increased organic in them via disc'd stubble or manure
Birds don't tend to feed on our shallow lagoons or seasonally flooded pools although they will roost on them, here there preferred food will be drown out
In the upper Humber invert density over most of the estuary is pretty low and therefore the curlew need these additional habitats to forage in and do seem fairly mobile at times to exploit different habitats (which may be different to those curlews wintering in the richer outer estuary). At the weekend I found 50 curlew feeding in winter wheat set into disc ploughed stubble but also feeding in the grass margins (see photo’s) I felt this nicely summed up the habitat the curlew are using away from the estuary.
So what does all this mean in terms of curlew conservation along the Humber? Well there is no doubt that curlew benefits from having organic rich fields where they can feed all along the estuary but particularly in the Upper Humber.
In my last blog I stated that the RSPB Humber team are keen to see grassland or organic rich arable created just over the flood banks to form a food rich strip between the estuary and the wider arable giving the curlew and other waders and wildfowl feeding opportunities close to the Humber, Ouse and Trent. We don't necessarily expect everyone to manage their fields like this but there is plenty of opportunity to increase it and also create new pockets of land in favourable condition for curlew and the likes.
Some greedy curlew from early this morning feeding on the recently sheep grazed and mown flood banks on the reserve - you can see them gulping down the soil inverts
Is this a big deviation from what happens now, maybe a little, but interestingly it is much more like what the Humber used to be back in the 1940's and 50's when the soil next to the estuary was too heavy to plow and was often grassland!
Hopefully with changing farming practices and a bit of habitat creation within this 'Middle Earth Zone' we can into the future give the curlew the wintering habitat it deserves - and just as a parting shot, curlew once bred around the estuary and still do on the nearby Wolds and areas out towards Doncaster, maybe into the distant future we can have them all year round.
I'll just add for those waiting for a sighting blog that I'll update on Wednesday if I have time - we have been and still are quite frozen up so for those wishing to visit I would suggest that you delay until I update you on Wednesday when hopefully the lagoons will have deiced!