Tuesday, 27 May 2014

Grazing - what a drag for Snipe

When is the best time to put grazing animals onto marshy grasslands with breeding Snipe?  We know that trampling rates of nests are high: on average 2.5% of nests are lost per day per cow per hectare.  So at a grazing density of 1 cow per hectare during incubation nearly half of all nests are likely to be lost to trampling.  Snipe can breed from April through to August if conditions remain suitable and later nests are more likely to be successful (early nests are more prone to predation), so the timing of the start of grazing is critical to Snipe productivity.

Recording drumming Snipe will tell you that they are likely to be breeding.  Last week we looked at some fields at the Ouse Washes where there were good numbers of ‘drummers’ in early April but had declined to just a couple on the most recent survey.  So is it now safe to put cattle onto the fields?

To see what was going on we met up with Rhys Green, who knows more about Snipe than most, to try out the rope dragging technique.  A 15mm rope was dragged slowly across the field over the top of the vegetation. ‘Watchers’ looked carefully for any Snipe that flew up as the rope progressed and then carefully checked that spot for nests or chicks.  Birds flying in advance of the rope were more likely to be feeding; those rising almost under the rope more likely to have a nest or chicks.

We found 3 nests and 10 broods. Chicks were measured, aged, ringed and returned before we quickly moved on. Eggs can be weighed and measured to determine hatching date.  Although only the female incubates, both male and female look after the chicks and supply food to them in the early days.  The male takes the first two to hatch, the female the latter two.  The chicks reared by the female apparently grow slower as she is in poorer condition than the male after incubation and provides less food to the chicks.  We noticed that Snipe with young often seemed to rise heavily from the ground with the tail feathers splayed downwards. A similar thing has been noted in Woodcock and may account for the belief that they can carry their young in flight.

So when to graze Snipe grasslands?  We know that trampling rates can be high during incubation, that birds can have nests or chicks long after drumming has ceased, and that eggs can be laid into July or even later.  If you value your Snipe, then start grazing late, at low intensity and only build numbers up from August. 

Photos: above - Snipe chicks and rope dragging.  Below - a typical squelchy area with tussocky, long and short vegetation that Snipe with chicks choose to feed in.


lizsnell said...

A most interesting piece. I live overlooking a raised bog NNR which is grazed all year in places and increasingly by large horses along the rushy fringes. We have been wondering why our snipe population has tumbled in the last 10 years and blaming all the predators attracted to this island of food. No hope of change because the graziers have ancient rights. The most recent signboards advertise this bog 'famous for its breeding birds'…choke.

Grumpy Ecologist said...

Thanks for your comment. Sadly Snipe are declining at an alarming rate. Grazing may be an issue at your site but it could also be other factors. Which NNR do you overlook?