Yes, lead is still a big problem, not just for curlews. That shouldn't be a significant factor in nest failures though.
Reading the stats for the nests, they are never going to be great. I read that they lay 4 eggs, 46% hatch & 26% are successfully raised (ie 1 chick per couple). Luckily they live 32 years!
I would say that if a long lived species raised one chick per pair per season, they wouldn't be in decline. Where are those stats from?
They came from Wikpaedia (French) fr.wikipedia.org/.../Courlis_cendr%C3%A9 & the relevant bit is "La femelle y pond 4 oeufs bruns-verdâtre incubés durant 27 à 29 jours2.
Seuls 46 % des œufs éclosent et parmi eux 28 % donneront un jeune viable2. C'est une espèce en déclin depuis plusieurs décennies2. La pollution des vasières, les marées noires peuvent affecter ses populations." However reading it again I think that the 28% is of the eggs that hatch which makes it half a chick/couple per year. Sorry!
I've read a lot of other reports about predation & although crows come out high in most studies, top of the list are ground based mammals. General opinion is that the most damage to their breeding is done by farmers cutting grass too early & therefore destroying the nest, loss of breeding areas, drainage of marshes etc etc. They are also still hunted in France around the coast.
Called up this Wiki page H & had it translated ... contains lots of interesting info ... came across a new word 'nidifugated' but can't quite understand what it means & whether it affects Curlew chicks adversely?
I had a look at the French version & they use the word "nidifuge" which means the chicks are born with feathers, open eyes & can move around as apposed to "nidicole" which is blind, no feathers & immobile.
I also found a big report which is really interesting, also in French, which gathers a lot of information from other studies https://www.ecologique-solidaire.gouv.fr/sites/default/files/PNG%20courlis%20cendre_v6_web.pdf . I'm not sure if it will translate or no.
Ah, so precocial as opposed to altricial?
Unfortunately the document will not translate ... 112 pages!!
It's a shame about the document as it's really interesting. One of the most pertinant pages is 38 which deals with predateurs. The UK study (Fletcher et al 2010) quotes figures on the high moors for Lapwing, Golden Plover & Curlew. The control of Foxes & Crow family tripled reproduction success & the areas controled showed an increase in numbers of 14% a year whereas the areas without pest control dropped by 17% a year. These stats are repreated by other countries studies. However nobody is quoted as just targeting Foxes & leaving Crows.
In Finland they did studies which showed that predation from artificial nests (79%) was twice that from their own nests (31%) & that out of all the predators Foxes & Raccoon dogs were responsible for the loss of 32%. Other predators mentioned were Hooded Crow, Magpie, American Mink & Ermine.
It would be interesting to know what other predateurs are in the areas where the Fox & Crow control took place.
Don't forget they are also culling Red Deer too as part of habitat management.
The Longshaw estate has always kept the numbers down to around 200 but I was told the other day when I went up there the RSPB have taken it much lower this year.
Deer are also regularly culled at Minsmere. Nobody likes it but too many birds would lose out if it wasn't done.