Tuesday, 21 September 2010

Stormie September

What was supposed to be just three days off Mousa, allowing a fleeting visit south for a wedding, turned into two weeks' (unwelcome) holiday from fieldwork. I had been warned that the weather is notoriously unpredictable and poor in September, so perhaps I should have known the risks of leaving the island, but I had been deluded by some of the best weather of the summer in the first few days of the month. The shorts even came out for just the second time all summer! After 16 weeks in the field, the enforced break did at least offer a touch of respite...hot showers more than just once a week, a kettle (much quicker means of making tea than boiling water on a stove!), no draughts coming in under the doors, fast internet, a sandy beach to run around on.... However, it did interrupt the regular monitoring of growth of Stormie chicks and I was left hoping that none would fledge before at least another set of measurements, and blood and feather samples could be collected from them.

Stormie chick tucked away in a nest site at the base of a dry-stone wall

Finally, the winds eased on Saturday, allowing the boat to comfortably cross Mousa Sound and moor safely at the jetty. A check of all study nests revealed just 3 out of 44 chicks had fledged. All these fledged within approximately 55 days, towards the lower end of the highly variable development period, which can range from 50 up to more than 70 days. The majority of chicks won't fledge until well into October. Most eggs that were still being incubated at the beginning of September have now been abandoned or the chick died within just a few days of hatching. Perhaps these late breeders are inexperienced birds? Are they just practising? Going through the motions of incubation but never with any intention of seeing it through to hatching or rearing the chick? The later a chick hatches, the harder it will become to provision that chick through the autumn.

This Stormie chick is partly-feathered, but the feathers are all still in pin (i.e. actively growing)
and a reasonable amount of down still remains

Good news is that all the chicks of radio-tagged birds are continuing to grow at a healthy pace; 3 are probably very close to fledging, while the other 3 will continue to be reared in the nest for a little longer. With no evidence of radio-tagging affecting a bird's ability to forage and provision its chick, we will look to expand the radio-tagging project next year to enhance our understanding about frequency and extent of movements of birds within the colony. A full update on the radio-tracking is to follow soon.  

Chick of a radio-tagged bird - the chick is fully-feathered with just a few tiny tufts of down remaining. With a tarsus length of 22.7mm, weighing 34.5g and with a wing chord of 109mm, this chicks must be ready to fledge virtually any day now.