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.

Tuesday, 13 May 2014

Pop-up wetlands

The idea of ‘Pop –up’ or ’walking wetlands’ has been used in North America for a number of years. They are temporary wetlands where land, usually agricultural, is shallowly flooded to attract waterbirds. This has achieved benefits for both conservation and agriculture. They have been used by conservationists to provide feeding habitat for passage waders or wildfowl. The large concentrations of Snow Geese or cranes that can occur on these sites are well known.
Why do we not seem to employ similar techniques in the UK? Okay these are not natural habitats but where feeding opportunities for birds are lacking, such temporary wetlands are likely to attract large numbers of birds.  We could adapt these ideas on nature reserves. Where a reserve lacks suitable shallow floods in the autumn but has available water, why not pump water up into a temporary scrape? Can we not flood cropped areas to provide autumn habitat for waterbirds?

Dungeness is already employing a variation of
this technique with some success. The
‘hay fields’ at Denge Marsh flood naturally with high water
levels but when they are low, water can
be pumped into the fields from the
adjacent ditches.  I took a trip down to ‘Dunge’ last week to look at these fields.  They have already attracted a flock of 10 Black-winged Stilts this year and a Long-billed Dowitcher was briefly present on the day of my visit. Sadly whilst I was enjoying the delights of 2 booming Bitterns, several Hobbies, Whimbrel, Common and Arctic Terns, the Dowitcher flew away.  Arriving at the hay fields, we discussed how management could be improved (to tempt Dowitchers to stay longer). This year, the fields will be drained by June in preparation for cutting the
 vegetation in early July and
 then several areas will be rotovated.  Water will be pumped 
back on in late July and the area 
maintained wet into next spring.  This
 should provide not only good early autumn feeding for
 passage waders and other waterbirds but also allow early colonisation by chironomids to enable a sufficiently large biomass of larvae by next spring for breeding waders.

Photos above: the hay fields at Dungeness, with Black-winged Stilt.