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Least Tern Invasion

posted May 19, 2011, 3:39 PM by Clemens Kuepper   [ updated May 19, 2011, 4:59 PM ]
Middle of May, the egg laying is most intense now. At Ceuta not only Snowy Plover are busy with their breeding activity but also other threatened birds. The salt works are home to a large Least Tern colony which is now buzzing with breeding activity. Least Tern are spectacular flyers and I really enjoy watching them diving for fish or shrimps in the small water bodies at Bahía de Ceuta. Over the last years this colony has been expanding. In 2010 we estimated the size to be 200 - 300 pairs. This is quite substantial  and good news for these threatened birds. This year we want to know it more exactly and therefore Felipe and Oscar, two students from Universidad Autonoma de Sinaloa are counting and monitoring the tern nests. This is not the easiest work. Terns are very aggressive at the nesting grounds. They seem to be so small when you watch them on the ground or in fishing, but they are very brave and attack intruders with spectacular swoops aiming at the head of the intruder. Walking among their nest is not really recommended. Getting close to their eggs even less. But Felipe and Oscar are tough field biologists and very enthusiastic! They found and marked already more than 100 nests. And many more pairs are courting and will be laying more clutches over the next few days. There is a real  Least Tern invasion this year at Bahía de Ceuta.

Of course, a few days after complaining in my blog last week that Snowy Plover breeding is late this year and that there are still no signs of chicks, the first chicks hatched. And yesterday the second clutch. Finally Snowy Plover broods! Broods are so much fun to watch and work with! The chicks are very cute. Fluffy small creatures, only about 6 g when they hatch, with far too long legs. It always amazes me that within a few hours after having worked so hard to come out of the egg, they are already running around and explore curiously their new world. Then the family will start to move to their brooding territory a few hours after the last chick hatched. This can be quite an adventurous journey. Snowy Plovers like to nest close to the water. But at Bahía de Ceuta the water levels are strongly fluctuating. If you nest is to close to the water it is easily flooded. But by now the water evaporates gradually. This means that by the time the chicks are hatching even if the nest was initially close to the water line,  water and food are now quite far away. The parents have to lead the tiny chicks to an area with enough food (spiders, insects, larvae, earth worms) so that the chicks can grow as fast as they can. The journey can be long, some family move up to 3 km during the first 24 hours of the chicks life. The journey is also dangerous, it often takes them through the territories of other Snowy Plover families who see the migrants as intruders and competors and there are lots of fights between families and nesting birds. The chicks are attacked frequently by the residents and can be severly injured. Not surprisingly a good number of chicks dies during this demanding journey.

For some families the journey is a lot harder because one parent has already deserted the brood. This leaves the other one to care for the chicks alone including the defence duties. This year in the two families that have already hatched the female was gone within 24 hours and the male has now to do all the hard work of bringing up the chicks alone whilst the female will be looking for a new partner to start a new family. The first family with Snowie 1 and 2 as parents chose a territory close to breeding Black necked stilts. These is  not the most friendly neighbourhood and one chick died already during the conflicts. Such tragedies happen frequently. However, yesterday, the field crew spotted the deserting female courted by a new male.

Love and death are very close together...