Tim Makrill - Project Officer
The April speaker was Tim Mackrill, Project Officer with the Osprey Project at Rutland Water. His talk covered the reasoning behind the re-introduction project, its progress so far, and the possible future for Ospreys in the Rutland area.
There are four subspecies of Osprey, two are sedentary in the Caribbean and Australasia, and two are migratory. Our subspecies is Pandion haliaetus haliaetus, and migrates to west Africa ? but may also winter somewhere en route - the other migratory subspecies breeds in North America and winters in South America. The Osprey is the only diurnal raptor that feeds exclusively on fish, and has talons that are supremely adapted for catching fish ? for example it can switch one of its three forward-facing claws to backwards-facing to help in grasping a slippery fish.
Young Ospreys normally hatch in late May, fledge in mid July, and are independent by late August. The breeding females generally start their migration in mid August, the chicks leave at the end of August, and the males leave when all their chicks have gone. Because the young birds migrate independently of their parents, the translocated birds are not at a disadvantage. The young birds are ready to breed at 3 or 4 years, at which stage the male birds will be the first to return to their natal area to establish a territory and start nest-building; they normally start to arrive in the UK in March. The females follow shortly afterwards but are less intent upon returning to their natal site; they can be attracted to a male who has established a territory elsewhere and is "advertising" for a mate. Immature birds may undertake a more leisurely migration, arriving in the UK a month or so later than the breeding birds, and may spend the summer at any suitable expanse of water. In other words, a summering pair do not necessarily mean a breeding pair for the future. For breeding birds, the spring migration is a very determined journey and they do not usually linger on their way unless they encounter bad weather. The autumn migration is more leisurely, and birds can sometimes spend a week or more in a favoured location.
Historically, the Osprey was widespread in England and Scotland (it is not known to have bred in Wales before 2004). However, the Victorians are well known for their persecution of raptors, and Ospreys did not escape this; the last English pair bred on the Somerset Levels in 1842. The situation in Scotland is less clear cut. There was no clear evidence of breeding in the period 1920-1954, but there were sporadic sightings during this time. In 1954, came the first confirmed breeding with the famous pair raising two chicks at Loch Garten. In the 1960s, the species began to gain a foothold, and breeding success really took off in the 1970s. Fifteen years ago there were an estimated 100 pairs, and now this has risen to an estimated 200 pairs. In some areas there are loose colonies of 10-15 pairs which have not expanded for several years, and are therefore assumed to be at maximum capacity. There is keen competition for nesting sites in these areas, and this can lead to aggressive behaviour and territorial disputes.
The Rutland Water reservoir was constructed in the 1970s, and comprises about 3000 acres of water and 17 miles of shoreline. It has all available conservation designations (RAMSAR, SPA, SSSI), and supports up to 20,000 wildfowl in winter. Such a large expanse of water is a clear attraction to passing Ospreys, and they were regularly seen there on migration in the 1980s. Two immature birds spent the summer there in 1994 and, after discussions between Tim Appleton the Reserve Manager, and Roy Dennis who has a lifetime's experience of monitoring Ospreys and other raptors, an artificial nest platform was erected during the winter 1994/5 (the construction of artificial nest platforms is an established and successful practice to encourage Ospreys to breed).
Regrettably, the birds did not return as hoped, although this was not entirely unexpected. Further discussion between Messrs Appleton and Dennis led to an application to IUCN (International Union for Conservation of Nature) for a licence to set up a re-introduction project using chicks from Scotland. IUCN have strict requirements for this: historical evidence of former breeding; clear understanding of the reasons for extinction; certainty that these reasons no longer apply; suitable habitat; introduced birds must be taxonomically similar to the original population; the loss of birds from the donor site must not be detrimental to that site.
All the requirements were met, so permission was given to remove 64 six-week-old chicks from Scottish nests: 8 were translocated in each of 1996 and 1997, then 12 in each of 1998-2001. During this time, Roy Dennis was carefully monitoring the Scottish populations to ensure that the loss was not detrimental. Of the 64 translocated chicks, 49 were males, and 15 were females, as it was believed that at least some of the male birds would attract females who had fledged from Scottish nests. However, this did not happen to the extent that was hoped, and the consequent surplus of unmated males at Rutland led to a decision to introduce a further 11 birds (9 females, 2 males) in 2005.
The translocated birds are released 2-3 weeks after arriving at Rutland, giving them about 6 weeks before migrating south. Fish was provided for the birds until they migrated (replicating what happens at natural nests where males feed their chicks until they leave), but some were seen to catch fish before departing on migration. During the post-release period the birds would frequently disappear for several hours at a time as they familiarised themselves with the area.
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In order to throw light on their migration routes, 13 Scottish birds, including 7 adults, and 14 Rutland birds (all juveniles) have been fitted with transmitters. Tim illustrated the benefits (for us) of satellite tracking by describing two migration journeys. The first was by a male who was translocated in 2000, and left Rutland on 2nd September. He passed west of the Brittany coast on the 3rd, and continued over the Bay of Biscay, making for northwest Spain. Very sadly, his signals disappeared as he attempted to come in towards land. Local birdwatchers in the area have given anecdotal evidence that Ospreys were often mobbed by Yellow-legged Gulls as they came in from the sea, and frequently forced down into the water and drowned. It was believed that this was the fate of this bird.
The second example was of a juvenile female from Scotland who was tracked southwards through Wales, Devon, and past the Brittany coast, but was then met with strong winds when making for Spain, and was pushed far out to sea. She made landfall 64 hours later in SW Portugal, an astonishing feat, and she stayed there for the rest of the winter. She has since bred successfully in Scotland.
Another formidable barrier to migrating birds is the Sahara Desert. Adults usually fly to the west, thus minimising the stretch of such hostile terrain that they have to cross. Juveniles sometimes fly south, right across the widest part of the desert and, of five juveniles who are known to have attempted the longer crossing, only one has survived.
Of the 64 birds originally released, 10 have returned to Rutland, and a further 2 males have bred in Wales. A small number have been reported dead, and the fate of the others is unknown. They could be living their lives in respectable obscurity in Scotland or elsewhere, since their whereabouts is only known if someone is able to read the coloured ring, and report it.
In the remainder of his talk, Tim gave details of the two translocated males who have bred successfully at Rutland. The first is known as 03(97). He returned in 1999 and 2000 as an immature bird, and then bred in 2001 and 2002, with an unringed female at a location away from the Rutland Water reserve. In 2001 they successfully raised one chick, but in 2002 were thwarted by exceptionally bad weather and, although at least one chick hatched, none survived the cold wet weather. In 2003 this female failed to return but her place was taken by a translocated female, 05(00), and this pair has bred every year since then, at the same site, and have raised 14 chicks over the five-year period. Both these birds are back together this year, and hopes are high.
The other male, 08(97), also returned in 1999, and every year since. Up to and including 2006, he attracted a succession of females but they all subsequently departed again - in 2006, the female left after the nest collapsed as she landed on it. In 2007, however, his nest was bigger and better, and he successfully bred with a Rutland female, 5N(04), and they fledged two chicks. Again, both these birds have arrived back this year.
A major point of interest, is the extent to which the Rutland-fledged young return and breed. So far, there have been no sightings of the chicks fledged prior to 2004 but, out of the 5 chicks fledged in 2004 and 2005, four have returned, so clearly the habitat is providing them with plenty of food to ensure strong healthy chicks. This year is looking good so far, with both of last year's breeding pairs back on territory, and expecting eggs shortly. Other (as yet unmated) birds are also present. Recent adverse weather has held up migrants further south, so other returning birds are expected.
For the future, the hope is that there could be 10+ pairs at Rutland, and other pairs could spread out to other water bodies not only in Leicestershire, but also Nottinghamshire and Derbyshire. It is also hoped to gain more knowledge of migration and other movements by the use of a new generation of solar-powered transmitters which should last for 3-4 years. In addition to the conservation benefits to the species itself, it is also beneficial to enthuse the general public with these birds. Persecution of raptors is only too well known, and anything that increases public awareness in a positive way must be a Good Thing.
Tim also summarised two other Osprey relocation projects in Andalusia in southern Spain, and in Tuscany, which have benefited from the experience gained at Rutland.
Tim was thanked for telling a fascinating tale, and adding a lot of interesting detail to the basic story. We already have Scottish birds moving through our area in good numbers, and perhaps we can look forward to an explosion of numbers at Rutland, and even have them breeding in our recording area one day!
For a lot of very detailed information about the Project, and about Ospreys in general, including their migration journeys, see the website www.ospreys.org.uk.
Wendy Thomson |
