|male Ruddy Duck|
Firstly a bit of history. About 70 Ruddy Ducks escaped from collections in the 50s and this dropped down to an estimated 20 birds by 1962. WeBS data suggests that there were 6,000 birds by 2000. Birds were first recorded in mainland Europe in 1965 and a wintering population of over 200 birds were recorded in France. That these birds eminated from the UK is indisputable as the French breeding population peaked at 20 pairs. Numbers peaked at 7 pairs in the Netherlands. By 1984 the first birds were recorded in Spain and between 1984 & 1999 a minimum of 139 birds were recorded in Spain at 43 localities. These must have been British in origin due to the numbers and genetic studies showed this to be the case (British Ruddies are a pretty undiverse lot genetically). So pre-cull we have Ruddy Ducks occuring at a rate of about 10/year in Spain and 6000 birds in the UK with maybe 100 other birds in the nations to the south of the UK. At this point there had been NO recorded vagrancy of Ruddy Duck in the eastern Atlantic. There has been a single subsequent record, of a female on the Azores in 2009.
|male White-headed Duck|
A brief look at White-headed Ducks shows that numbers dipped to 22 pairs in the seventies but thanks to the protection of a number of sites they currently number 2,600 pairs approximately. This represents 25% of the world population and all of the European population. Birds are restricted to sites in the south and east of the country and breed in emergent vegetation fringing small eutrophic lakes. 84% of birds breed in protected areas.
Now a bit of biology. Ruddy Ducks outcompete male White-headed Ducks when they share territory. Ruddy Ducks are preferred by female White-headed Ducks to the males of their own species. In addition Ruddy Ducks are more aggressive when courting making them more likely to win an territorial battles for females. Thirdly, unlike White-headed Ducks but in common with many duck species, Ruddy Ducks will have forced intercourse (rape) with females including female White-headed Ducks. Basically when in direct competition Ruddy Ducks win hands down against White-headed Ducks when it comes to breeding success. And here is the shocker - hybrids are viable to at least the third generation. Those Ruddy genes are in the population and not getting out. So the big question is then - would it happen in the wild? Well 59 hybrids were recorded to 1999 at 23 different sites. Thats a lot. Ruddy genes are not thought to have introgressed yet as culling of Ruddy's and hybrids occurs in Spain but it only takes one or two broods to remove pure White-headed Ducks from a discrete area by introgression. I have heard people say - why cant we just cull birds in Spain. They do but Ruddy Ducks kept arriving and as mentioned above due to the viability of hybrids the gene pool would quickly get diluted by Ruddy genes if any were missed - better to treat the cause at source. Eradicate alien Ruddy Ducks.
Now for some politics. The UK is part of the EU and as such is a signatory of the EU birds directive (you know, the one we use to berate Malta about) and as such we are bound by the Bonn and Bern conventions. We are also a signatory to the African-Eurasian Waterbirds Agreement (AEWA) which includes White-headed Ducks. This means we are legally obliged (and rightly so) to conserve birds named in these agreements (which White-headed Duck is). I have heard people moan about shooting of the Ruddy's but a feasibility study showed that oiling eggs and other measures were not effective due to the population size. The Ruddy Ducks had to be removed. That is killed if you dont dress it up.
So in summary. We let Ruddy Ducks become established. They did. They went to Spain. They outcompeted the recovering White-headed Ducks and threatened to dilute the gene pool as hybrids were viable. We eradicated (more or less) Ruddy Ducks through shooting. White-headed Ducks are significantly less threatened. Where is the problem? There are plans to clean up the few remaining in Britain and the near continent. Is LGRE upset about the loss of a year tick? Maybe when White-headed Ducks have spread to the camargue and western France and are regular vagrants he will be less vehement? I support the cull. Do you? If not why not?
Study for Possible Vagration