If they get the opportunity, young male Ospreys will breed as early as four years of age. 03(97) is a good example. He first returned to Rutland as a two-year-old in 1999. He built the nest that we now refer to as Site B a year later and then raised a single chick with an unringed (presumably Scottish) female the next summer. Since then (including this year) 03 has gone on to rear a total of 27 chicks with three different females.
Not all of the Rutland Ospreys, though, have enjoyed the same level of success. 09(98) was translocated to Rutland Water in 1998 – a year after 03. He returned for the first time two years later, but a further twelve summers passed before he finally paired up with a female; 5N(04) at Site N.
Knowing him so well and having followed his 6000 mile return migration to Senegal this winter, it was great to see him breeding for the first time this year. It was especially exciting to be at the nest a few weeks ago, when the first chick hatched.
As soon as their chicks hatch, adult male Ospreys have to work very hard to keep up with the insatiable appetites of their chicks. We were particularly interested to see how 09 would react to having hungry chicks to feed – it was something he had never faced before. Having equipped him with a satellite transmitter last year we were interested to see how his fishing habits would change with this increasing demand; the great thing with the new GPS transmitters is that they provide data every hour, thereby enabling us to build-up a detailed picture of each bird’s movements.
As we expected, 09 has generally favoured Rutland Water for fishing, but has visited a number of other sites too. One notable feature of his daily fishing movements, is that he rarely visits the same site on successive fishing trips. A quick look at the last ten days shows that he has visited at least five different sites, away from Rutland Water, but none more than five times. This kind of information is of great conservation value; not least because it will help us alleviate any fears fishing lake owners may have of the potential impact of breeding Ospreys. Even when they have chicks, 09’s data suggests that the birds will never have a major impact on fish stocks.
Without the aid of a camera looking into the Site N nest, it was a couple of weeks before we knew how many chicks were in there. Eventually it was possible to make out the heads of two chicks – a great outcome given that 09 has never bred before. In the intervening six weeks the two chicks have developed well and at the end of last week we visited Site N to ring them.
It was immediately apparent that both chicks were in excellent condition and this was confirmed when we weighed them. Both weighed 1510g – an excellent weigh for male chicks, which their head structure and bill size suggested they were. Having watched 09’s repeated failed attempts to attract a mate and breed each summer since 2000, it was a real privilege and very memorable to see his first two offspring close up.
Having ringed the chicks with blue colour rings on their right legs – OF and OJ – we put them back in the nest. As we were driving away 09 arrived with a fish and landed on the nest with the rest of his family. It seemed a very fitting end to the evening.