Friday, 25 September 2015

Tipping the balance

There often seems to be an assumption that if birds are going to colonise the UK, then it will just happen.  However, successful colonisation is by no means inevitable and some species may need a lot of help to do so.  In addition, these newcomers often seem to be valued less than declining ‘outgoing’ species, but why should colonising species be less important than those declining?  If their range is shifting in our direction as a result of deteriorating conditions elsewhere, their conservation needs may be just as important.

Black-winged Stilts are a good example of a species ‘heading our way’.  There has been an increase in breeding attempts by stilts in the UK in recent years. Unfortunately, Black-winged Stilt productivity in the UK has been poor.  There have been 13 nesting attempts since 2005, six have hatched young, and these 13 nesting attempts have fledged just seven young (all last year).  So, this amounts to an overall productivity of just 0.54 young per pair.  By contrast, it was a pretty productive breeding season for stilts in the Netherlands last year, and the ten nesting pairs there fledged 26 young (2.6 young per pair).

This year, 2 pairs of Black-winged Stilts attempted to nest at Cliffe (photos below).  They failed to rear any young, despite a considerable amount of effort, including a predator control plan and a 24-hour watch.  The young chicks were unfortunately predated by Black-headed Gulls within a few days of hatching.  This has however, provided much useful information about how to deal with future events.  The key is to act fast when birds arrive and put in place all the necessary protection.  However, a more forward thinking option is to attract the birds into safer nesting areas by improving the habitat.   In short, we need to tip the balance in their favour.  Such actions will also benefit other key species using the same habitat, such as Avocets and terns.

The Great White Egret is another species currently in the early stages of colonization of the UK.   There are interesting lessons to be learnt from the colonisation of The Netherlands.  Numbers remained low for some 25 years at the colonisation site, the Oostvaardersplassen.  The trigger for an increase in numbers was the creation of a range of shallow water feeding grounds within range of the breeding site in the late 1990s   These shallow, clear waters are of importance to the egrets for feeding especially in the first part of the breeding season.  Chick production increased steeply after the creation of these areas and breeding numbers dropped in years when they were dry.  However, these changes allowed GWE to increase from less than 5 pairs in the 1990s to 143 in 2006.

We have tried to apply the same thinking to GWE colonization of the UK.  Where are the likely breeding sites?  Is there suitable nesting and feeding habitat? If not, can we put it in place?  The quality and quantity of food available to the birds is critical to both initiating breeding and breeding success.  In the UK there is a lack of suitable feeding areas around many of the likely breeding sites but with some thought this could, and is, being addressed.

In Somerset, the initial breeding was triggered by the creation of large reedbeds and then appropriate feeding areas bringing the birds into nesting condition.  Two or three pairs have bred annually since.  This year the provision of a high quality feeding area has coincided with a jump to 6-9 pairs. On a visit to the site in June, one feeding area contained 78 Little Egrets, 13 GWE (and a further 5 flying around) and a couple of dozen Grey Heron. Later in the season, another area provided feeding for fledged juveniles (photo above).

So, species may want to colonise, but the conditions may not be ideal.  We should be looking for opportunities to tip the balance in their favour.  This is of course no more than a decent reserve warden should be doing – thoughtful management of habitat to get the best result.