Tuesday, September 17, 2013

The Tree Swallows (Tachycineta bicolor) on Middleton Island in 2013

2013 was the fifth year of the Middleton Island Tree Swallow (TRES) Project, after the first nest boxes were put up there and got occupied by swallows in 2009. More about the history of the TRES on Middleton Island and the earlier years of this project can be found in a previous blog post: http://www.middletonisland.blogspot.pt/2012/09/the-tree-swallows-tachycineta-bicolor.html
Last year I wrote a short story about the TRES on Middleton for the annual report of 'NESTKAST', a Dutch network of amateur and professional nest box researchers. It's written in Dutch and can be downloaded here: https://www.sovon.nl/nl/content/nestkast-jaarverslag-broedseizoen-2012

My expectations for this breeding season were not very high as, although the population has shown a gradual increase during the first four years, during the previous year (2012), due to poor weather conditions, only very few chicks fledged. This year again volunteers of the Institute for Seabird Research and Conservation (ISRC; formerly USGS) put effort in monitoring the nest boxes.

After receiving this year’s results I was quite surprised. Based on the data they gathered I suspect that no fewer than 10 boxes were occupied; double the number that was in use by swallows in 2012! Unfortunately, halfway the breeding season the attention of the volunteers decreased and not all boxes got monitored. I suspect that they were too busy with their seabird projects this year, and with an increasing number of TRES there will also be a lot more time and effort required for this project. Possibly because of this, the results that are shown below come with a number of question marks. (Strangely, I did not get a reply on further inquiries about the TRES work this year from any of them. And no photos from this breeding season either… (Alan, Erica and Lorraine??)).

Thankfully the volunteers still managed to band a total of 17 chicks from three boxes. Whether attempts of four other pairs resulted in ‘bandable’ young or not, remains unknown. Unfortunately also, this year by the end of the breeding season the nest boxes did not get cleaned and old nests were not inspected for any unhatched eggs or deceased chicks. Therefore it is difficult to say something about the TRES’ fledging and productivity for 2013. Unfortunate also because when nest boxes are not cleaned before the winter, the boxes' life expectancy gets several years shorter, which is my experience.

I suspect that many young will have fledged as the weather conditions during the end of June and early July were not too bad, although not perfect either (I recently found a new website with what seems to be a rather accurate (historical) weather report from Middleton: http://rp5.md/Weather_archive_in_Middleton_Island_%28airport%29). I will try to see if the nest boxes still can get inspected and cleaned before the winter (preferably) or before the new breeding season starts.

Recommendations for the following year(s)

With a continuously increasing number of TRES utilizing nest boxes out on Middleton Island, the project could be considered a success. However, still very little is known about the origin of the swallows that nest there. As part of this project  a total of 3 adult and 41 chicks have been banded there up till now (of which at least 7 chicks died before fledging), but no (or barely any) effort has been put in resighting these birds as possible nesters on Middleton. Therefore it remains unknown how the remote Middleton Island population is made up and what the true value of this project would be. A continuation of the banding effort is a must, but capturing and resighting breeding birds has become equally important.

Additionally, with a rapidly increasing number of occupied nest boxes out there, chances are that in the very near future the number of present boxes will become a limiting factor for the developing population. With 10 out of 17 boxes in use, the housing market for TRES still appears to be open. It can be expected, however, that some pairs will exclude birds from a neighboring box. This is visible on the map to some extent, as the swallows appear to have a preference to nest away from each other. It will probably be better not to wait until all of these 17 boxes in use (which I doubt will ever happen). Several additional nest boxes will have to be installed within the upcoming two years, I suspect.

To me it has become obvious that during the upcoming years this project deserves more attention, as well as effort being put into it. There might be a lot to learn from these little birds on Middleton Island.

Acknowledgements: I’d like to thank the ISRC volunteers for putting effort in monitoring the TRES population to the extent that they did, Kyle Elliot again for giving some valuable instructions at the start of the summer, and Scott Hatch (ISRC) for allowing the volunteers to be busy with something other than seabirds.

1 comment:

  1. http://www.alaskamagazine.com/magazine/table-of-contents Nice article about Middleton in here. Nice blog you've got.