There’s a very curious news item doing the rounds this morning that seems to have originated from an SNH press release. The news is that two immature female golden eagles have attempted to breed in two different locations and that this is somehow an indication of a potential ‘upturn’ in the fortunes of the Scottish golden eagle population.
To the unassuming general public, the news that golden eagles are breeding at an earlier age than normal (3 years old instead of the usual 4-6 years) may well sound like a positive story. On a superficial level this is probably true – breeding golden eagles, at whatever age, has got to be good news, right?
According to several scientific studies, the occurrence of breeding subadult eagles should actually be used as an early-warning of potential population decline. The reason these Scottish golden eagles are attempting to breed at three years of age is because there is little or no competition for that vacant territory. Why is there little or no competition? Because one or both of the territorial adults have been killed and there are very few non-breeding adults (known as ‘floaters’) around to challenge for the territory. If the population was healthy, it would be these breeding-age floaters that would move in to the territory, not an immature three-year old bird.
An excellent study (Whitfield et al. 2004 – see below) has also demonstrated that subadult and mixed-age breeding golden eagle pairs in Scotland have lower breeding success than adult pairs – a result of inexperience and persecution, seeing as most golden eagle territories in Scotland with subadult breeders are in areas associated with illegal persecution.
Des Thompson from SNH does mention the link to persecution in this press release but he kind of glosses over this and instead suggests that these young breeders are good news. They are good news as long as they are not bumped off, and the chances of them being bumped off is quite high because, as mentioned above, these territories with immature breeders are only available because the adults have already been persecuted.
Instead of spinning this as a ‘good news story’ and ignoring the known warning signs of a population in decline, SNH should be telling us how they are going to beef up their conservation efforts at these sites and get the Scottish golden eagle population back to a favourable conservation status – as it is, it is far from that.
Here is a PDF of the scientific study mentioned above, entitled The Effects of Persecution on Age of Breeding and Territory Occupation in Golden Eagles in Scotland: Effects of persecution on age GE