Here is a translated copy of an e-mail from Carsten Rohde, to our member, Leonia, who has given permission to post it here.
With thanks to Carsten Rohde and Leonia for making this information available to us.
BLACK STORK SURVIVAL RATES
Dear storkaholics of the world!
Remember that I mentioned a mail by Carsten Rohde on the question of the rate of surviving storklets in their 1st calender year. I now tried to manage the translation of this mail.
». . . Coming to the issue raised by you concerning statistically validated values for death rate of juvenile blackstorks in 1st calender year (cy):
There are no hedged investigations – how should that be. We cannot f.e. provide all young birds with transmitters . . . .
Yet the banding and transmitting may and will bring some interesting results over the next few years.
Drama of course, is the fate of the storks from Estonia (out of a number of 5 storklets is only one still remaining).
We all know that dangers are already lurking in the neighbourhood of the nest during the migration. Landing on power lines and electrocution unfortunately are usual for storklets. But other causes too are not seldom, though we are not always able to identify immediately.
This year I have banded 63 young storks – including 36 in Mecklenburg-Vorpommern (MV). Of those 36 storklets I already know 3 cases, where the young storks did not reach a radius of 100 km, but had already failed. Two of those were probably landings on power lines (one of them from the nest in the old oak tree on the foto) and an ambiguous case. The bird was found dead at the edge of the forest (no malnutrition, no hint victims) - I have submitted the bird to Berlin (for section). I suspect poison (unfortunately hard to detect) or even prey of a "hunter" (what we are able to detect). But of course we first must wait for the result of the section and should not make hasty presumptions. Besides all it was very suspicious that the finder previously discovered a dead buzzard nearby. Unfortunately, I have received that information too late - otherwise I would have involved the buzzard too.
So already a loss of 8% close to the nest in MV, which we immediately could identify because of the banding. Unpredictable is the estimated number of undetected cases - but I guess because of long experience, that the death rate in MV in the sector of 100 km around the nest in young birds will be already at about 15-20%. In other regions with different structures (as mountain areas with tributaly valleys or dangerous power lines) that value may partly still be higher. Although so far only one case of a victim of a wind turbine is known (Hessen), there is as I know a not insignificant number of unrecorded cases. There are veritable bulwark structures located specificaly on migration routes (but even in the nesting areas as well).
Besides that I know about unfortunately high evidence of death rates in Israel. As there are collisions with power lines, electrocution, poisoning, and victims of nets (nets across fish ponds), all of those are everydays somber loss report.
According to my calculations there are 20,000-22,000 black storks migrating through that area!
So by concerning the hazards there, the cases I found there and experience gained from previous years and also that there are no systematic investigations in Israel (who cares about electrocution) I would figure the annual losses by at least 250-300 storks (predominantly white storks) not including pelicans and birds of prey. The unknown situation in the coastal region not to be mentioned!
Especially the evening approaches of about 20,000 to 50,000 white storks in the Beit Shean Valley in August are problematic. The storks fly into these territories in twilight and are searching for resting places. And one can only find a smal part of those who died there (because of lots of predatory mammals).
Also there is a very large deficit to catch up. We do not really understand why the hazards are not reduced in Israel since many years, although the AirForce is financing the counting of the birds. And it would be possible to change things without much effort . . .
Especially for the black stork I figure the anual losses of young birds on an average of about 20 indivuals because of powerlines (unfortunately they have their sleeping places there). And if you have watched them approaching, you may wonder how they survive.
Not to forget the victims of the network above the fish ponds, were several storks are losing their lives every year. I already do find about 5-10 storks every year during those 2-4 weeks! So you may start a projection . . The Israelis have estimated the losses much too low (f.e. only 40 storks).
The photos I sent you [they are not added here] - like a young stork in panic swimming within a pond underneath a net (October 2008), 1 dead young stork in the net (Sept. 2004), 1 elder stork shot (March 2008), victim of power line (a white stork Sept. / October 2008) and roost on power line pylons (March 2008). These are representative examples of many other unnecessary victims .... You could go insane: we are fighting to preserve the breeding and feeding areas - the youngsters are fledging successfully and then ......
Looking even further on the hazards along the migration routes (making leeway, bad weather, poisoning, food shortages ....) and then have a closer look at the winter quarters in Africa - there will not be many young storks left.
Conclusion: On my experience and a critical analysis of all the information I got I would assume that the death rate among storklets (in this case black stork) during their first year will be 70-75% in the annual average. For blackstork in 2nd calender year there will be losses too.
Probably there will be a blackstork survival quote of about 15-20% in one age-group for breeding succession or colonization of new area (now that there is evidence about blackstorks breeding in 3rd c.y.).
This is a very low value for this relatively small Eurasian stock. There are not much better values for white stork. . . .«
I have to say many thanks to Carsten for the detailed answer he had given although he is still very busy with the evaluations of his research. Furthermore, I must once again express my admiration for the year by year work of all nest supervisors (incl. Urmas, Carsten, Maris Strazds!