Wednesday, 15 July 2015

Dinner time!

This week on Rockabill we'll be doing the second of our all-day feeding watches to gather important data on the food our Roseate chicks are being fed - that is, what types of fish the adults are bringing back and the rate they're supplying them at. We start at 5am and finish at 10pm, taking it in shifts to account for all food items brought back to around 25 of our Roseate Tern nests. Later on in the week we'll be doing similar studies for Common Terns as there is usually a slight difference in the food they manage to get.

This kind of data has been gathered every year on Rockabill and so we've amasssed a very informative long-term dataset that will help us learn more about the Terns, their preferences and what they rely on. 

Check out these short videos below of Tern chicks being fed:

First, one of our oldest Roseate Tern chicks comes running out of its box to greet an adult with food:


Next, a hungry Common Tern chick beats its sibling to the incoming food:


Many of the small fish the Terns feed on are also eaten by the larger fish that humans eat. While there aren't enough Terns to have an impact on the numbers of those small fish, the Terns act as an indicator species for the larger food web in the Irish Sea - if they can't find small fish to eat, then neither can the bigger fish and that could help explain declines in commercially exploited fish. Sometimes these are short-term problems, sometimes they're longer-term changes like overfishing or the knock-on effects of climate change.

Common Tern coming in with a sandeel (BB - picture taken under NPWS license)
Common Tern delivering food to hungry chicks (BB - picture taken under NPWS license)

Roseate Tern with a sprat (BB - picture taken under NPWS license)

Here are some of the fish species brought into the colony by adult Terns:

Sandeel (AP)

Pipefish - they offer no food value to chicks and can be a choking hazard! (AP)

Clupeid - the most common prey species (AP)

Stickleback (AP)

One of the more colourful food items brought back to the colony!

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