One of the quotes from today’s RSPB Birdcrime report is;
‘Natural England holds a wealth of data from hen harriers tagged since 2007. We have recommended that the Government commissions an independent investigation of these data to help determine where and why tagged hen harriers and other tagged birds of prey are disappearing.’
Well, there is an alternative way forward for the RSPB. In response to FoI requests Natural England gave me the following response in September 2015:
7. What would be the process of obtaining copies of the data for personal scientific analysis? It has, unfortunately, taken longer than originally envisaged for data collected through the HHRP over recent years to be analysed and the results published. It remains our intention to carry out this work. However, we would be open to proposals from bona fide researchers to further utilise the large amounts of data that have been collected through the programme. Because of concerns over the sensitivity of the data (referred to above) any proposal would be considered on a case by case basis and we would require the appropriate assurances over data security. We would need to reach agreement on the nature and timing of subsequent publications to ensure that these did not compromise the data analysis that is already underway.
So, all the RSPB has to do is to ask for the data and they can analyse it.
This would be well worth doing.
All sorts of analysis are worthwhile. Here are some ideas.
Let’s just take the 15 Hen Harriers satellite-tagged last breeding season.
Six of them are still alive (Aalin, DeeCee, Finn, Harriet, Wendy, Sorrel) – unless something has happened to them very recently.
Three of them are known to be dead (Rowan, shot; Hermione, natural causes; Carroll, parasites but did contain two shot pellets).
The remaining six have disappeared and are thought to be dead but maybe some might be flying around still with failed tags (Beater, Bonny, Brian, Donald, Elwood, Tarras).
According to the BTO, and just for interest, the proportion of fledged Hen Harriers surviving for two years is around 22%. That’s more or less equivalent to 50% survival each year – after two years you have 50% of 50% which is 25% (as near as damn it = 22%). So, in June we might roughly expect seven or eight of last year’s 15 fledged and tagged Hen Harriers still to be alive (although I think we would expect mortality to be higher in males than females). Well, June is four months away and we are already down to just six birds. Etheridge et al (The Effects of Illegal Killing and Destruction of Nests by Humans on the Population Dynamics of the Hen Harrier Circus cyaneus in Scotland. B. Etheridge, R. W. Summers and R. E. Green. Journal of Applied Ecology Vol. 34, No. 4 (Aug., 1997), pp. 1081-1105) estimate first year survival of females to be 36% (with wide confidence intervals) from wing-tagging studies and if only one more of the 15 dies/disappears then we are in that ball park. With all the tagged birds over the years of the NE Hen Harrier study we could get much better estimates of juvenile survival – normally a difficult thing to measure.
Then there is that tricky question of where are Hen Harriers at most risk. Might it, just possibly, be when they are on grouse moors other than Langholm Moor? Well, using the locations of tagged Hen Harriers and relating them to habitat data from satellite imagery, it should be possible to estimate risk of death (or sudden disappearance) on a habitat basis. That would be jolly interesting don’t you think?
There are plenty of other potential analyses, each with their challenges, but we haven’t seen any of this come out of Natural England so far. I’d back the RSPB to get some really useful information out of this dataset inside six months. They should ask for it. And NE should supply it.