Sunday, 6 July 2014

Food for Thought

For the last two Saturdays we've been taking it in turns to watch a number of Roseate Tern nests and record each feeding visit - the time, the box and the chick that got the food, the species of fish and the size of the fish ( in 'bill-lengths') - starting at 5am and continuing on until 10pm. Now I know what you're thinking - that sounds like a long day; what in god's name would make you do that? And the short answer is . . . . . . . . . our boss told us to!

Common Tern siblings fighting over a Sand Eel! (Picture taken under NPWS license)

The longer answer is that it provides important information on the food the chicks are getting this year - if productivity (i.e. the number of chicks that fledge) this year is low, we can look back at our data to see how this year's feeding was compared to other years - if there were less feeding visits than other years it could indicate that food was harder to find this year, if there were less of the birds preferred species and more of other species they only occasionally feed on it could be that food availability was poor this year, or if the food items being fed to the chicks were small compared to other years then maybe the quality of fish available was pretty poor. Given how important food availability and quality is in the survival of any birds - especially chicks, and especially to large colonies of birds/chicks - this is very important information to gather every year. Even if this year's productivity is okay it will provide a useful comparison for any poorer years in the future - more data that we can gather to help inform the future monitoring and conservation of the Roseate Tern.

Roseate tern with a Sand Eel to feed to it's chicks. Sand Eels are one of the most common food items for Irish Terns and other species such as Puffins and Kittiwakes. (Picture taken under NPWS license)

Roseate Tern adult with a Sprat to feed to it's hungry chicks - another common and important food item for Terns and other seabirds in Ireland. (Picture taken under NPWS license)

Unfortunately a lot of second and third chicks in Common and Roseate Tern clutches have died over the past week, despite the weather being largely favourable, so it could be that the adults are finding it harder to find suitable food in the area. The chicks weigh less than 100g for the first two weeks of their life, so any food shortage leaves them weak and unable to cope with cold or wet conditions. 

We have one more Roseate food watch and a few Common Tern food watches left to do before we have a complete dataset for the season. Fingers crossed the weather doesn't get too bad over the next week or two and that the adults manage to find enough food to keep the chicks going until it's time for them to fledge later this month!

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