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.

Weather for ducks

Until the recent deluge, it appeared that another dry spring was upon us and the focus of reserve visits recently has been on the efficiency of water management.  Although concerns about the effects of the drought on wetlands and wetland birds have been somewhat over-hyped, it is certainly worth thinking about how we manage our water resources, particularly in relation to changing climatic patterns into the future.  On many sites, water is simply allowed to drain away; maybe not a problem in a wet year, but in a dry year perhaps making the difference between a poor and reasonable breeding season.

Visits to Old Hall Marshes and the Ouse Washes were on the agenda for last week.   Both are tremendous sites for waders but they face differing issues.    Old Hall is located in one of the driest parts of the country and frequently struggles to maintain enough water, whilst the Ouse Washes have been suffering from excessive summer flooding in recent years.   At Old Hall, a total of around 250 pairs of Redshank, Lapwing and Avocet breed.  It is also a great site for passage and wintering waders, although the day I visited was not the best; a couple of Spotted Redshanks, 30+ Whimbrel, 50+ Black-tailed Godwits, Ruff and LRP.  Summer migrants were represented by a few Common and Arctic Terns while the last couple of dozen wintering Brent Geese were still on the saltmarsh.  The Ouse Washes support around 500 pairs of waders, notably 140 pairs of Snipe.  Plenty of drumming birds were evident on my visit with added interest provided by Garganey, Ruff and Black-tailed Godwits.

Where water availability is a problem, the key to success is a clear understanding of the water budget – the annual inputs and outgoings.  The annual rainfall at Old Hall is a meagre 577 mm, with a mean summer moisture deficit of 110mm.  So, all available excess winter water has to be stored to offset summer losses through evaporation and transpiration.   Excess water is taken from the Salcotstone Brook which flows through the reserve and out into the estuary.   The water is stored in the fleets, borrow-dykes and reedbed, with wind pumps moving this water into the key wader areas as required.  Breeding wader areas may be allowed to dry from July onwards but areas such as Bale Field and Pennyhole Bottom require water into the autumn wader passage.  Old Hall remains below target water level this spring, so the recent rain is welcome.  By contrast, the Ouse Washes were looking superb in the ‘drought’.  After the weekend’s rain, the site is flooded bank to bank.  Good for ducks, not so good for waders.

Rights of passage

Passage B-t Godwit, Ouse pool with waders, Cranes - "don't look now but is that a Fox?"

Look, all I want to do is go out locally, visit a little muddy pool and see a few passage waders. Is that too much to ask? Well evidently it is. The water is either too high or too low, or it’s bone-dry, or overgrown.
Travelling around a number of sites over the last week, I was struck by the lack of good quality wet habitat for waterbirds at the current time. Okay, it has been a dry spring and water is in short supply despite the recent rain, but there seems little or no attempt to even try and create shallow wet habitat with muddy margins.

Have we forgotten about the importance of feeding stop-over locations for passage waterbirds?

Food-rich, shallow wetland habitats are important for wetland birds prior to, or during, migration. Birds have differing migration strategies and will use these wetlands in different ways. This was clear during the recent trip to the Netherlands when Jan van der Winden's discussed his fascinating research into Purple Heron ecology. After breeding, Purple Herons spend a month or so in a favoured feeding area to put on weight before migration. They remain within this rich feeding area, roosting nearby. With a fast, long-distance flight to follow, good feeding areas are critical at both ends of the journey. Other species will use wetlands to ‘re-fuel’ along the way, with shorter flights between stop-over sites. Birds that reach the most productive of these sites may move on in a relatively straightforward manner towards the wintering areas. On the other hand, birds that miss the main sites or encounter difficulties in ‘re-fuelling’ , either because of low quality habitat or food depletion by preceding birds, need the option of alternatives before moving on. A complex of stop-over sites through the flyway is therefore essential.

Okay, so there are a number of large, mainly coastal, sites that cater for passage birds (not necessarily all in good condition), but the range of alternative options in the wider countryside is sparse. Yet on nature reserves that might be expected to provide such habitat, provision seems mostly incidental rather than a deliberate and thoughtful attempt to provide good quality habitat. It does not appear to be a conservation priority. Surely this is wrong.

A visit to the Ouse Washes at last delivered some reasonable habitat. A muddy pool supported 24 Ruff as well as Avocet, Dunlin, Redshank, Lapwing and Green Sandpiper. The next pool had Shoveler, Garganey and Teal. Nearby, 3 Cranes eyed-up a young Fox before chasing it up the bank.

Ouse up and Ouse down?

The Ouse Washes are officially classed as ‘Unfavourable’ condition, due to the increased incidence of summer flooding and the poor water quality. Breeding waders have declined, from an overall total of 900+ pairs in 1990 to around 450 this year. Most notably, Black-tailed Godwits have declined to just 2 or 3 pairs at this former stronghold, and Snipe have also declined sharply.

However, ‘every cloud has a silver lining’ as they say. Under the wetter summer conditions, breeding duck have increased, with average counts over the last five years of 161 pairs of Shoveler, 110 of Gadwall and 9 of Garganey. Spotted Crakes also increase in the wetter years, with up to 4 ‘whippers’ in recent times. These ups and downs mirror the cyclical patterns of species seen in some natural floodplains in Europe – more ducks, grebes and terns in wet years, more waders and Corncrakes in drier years.

The influence of the water regime also applies in the winter, deep floods favour Pochard, Tufted Duck and Coot, shallow floods favour the dabblers; Shoveler, Wigeon, Pintail and Teal.  The highly mobile birds respond rapidly as the water levels change.  There are of course many external influences at work as well. Many wildfowl are ‘short-stopping’ on the continent, due to recent milder (!?) winters. The wild swans, perhaps the washes most notable winter visitors, also show differing trends, but this is not down to water regime. Whilst Whoopers (from Iceland) have steadily increased to over 5,000, Bewick’s have declined to around 3,500. The decline in Bewick’s is concerning as it is clear that poor breeding success is at least part of the cause. The number of juvenile birds accompanying the adults has sharply declined in recent years.

Today the washes were frozen stiff. Whoopers and Bewick’s fed out in the adjacent beet fields, returning in the late afternoon to roost on a small area they keep ice-free. Around 1600 have returned so far this winter. It may be ‘unfavourable’ but the Ouse Washes are still a fantastic place for birds.