By Susan Heath
Twice this week we saw oystercatchers chasing Crested Caracaras away. In my four years out there on the bays I haven’t seen that many caracaras on the islands so it didn’t occur to me that they could be a predator of oystercatcher chicks, but the oystercatchers clearly see them as a threat so maybe they are. We’ve seen oystercatchers become aggressive with a growing list of avian threats including Laughing Gull, Great Blue Heron, Ruddy Turnstone, Peregrine Falcon, Crested Caracara, and Boat-tailed and Great-tailed Grackles. In several spots we suspect that eggs are being stepped on by Brown Pelicans and we witnessed a standoff between an oystercatcher trying to incubate its nest and a Brown Pelican that attempted to walk too close to the nest. The list of threats is immense and sometimes I wonder how they ever succeed.
On Monday we checked again on the pair with three chicks. If you remember we thought one of the chicks might have an injured wing but this week we saw that very chick take a short flight across the island where it was hatched so all appears to be well. We had hoped to band another chick this week but when we arrived at the nesting site on Monday, the adults were there but there was no chick with them. It is rare for a chick this old to disappear but it does happen occasionally. We weren’t able to go check on it again on Friday because we spent the day running from thunderstorms and weren’t able to get to all the nesting islands.
Speaking of chicks, here’s a shot of the next ones to get banded. They are about 25 days old now and we try to band them between 30 and 35 days so next week we’ll round ‘em up. These chicks are special to me because one of their parents is a bird that Sasha (the previous grad student who has now gone on to bigger things!) and I banded as a chick in 2011. This is the first year that birds we banded as chicks are old enough to breed and this is the first one to have chicks old enough for us to band this year. That’s pretty exciting to me!
On a sad note, when we checked on the birds in Drum Bay this week we noticed that CH, a male that we banded earlier this year, had something lodged underneath the skin on one of his legs. Whatever it was was sticking out at an odd angle. The bird was limping and obviously in jeopardy but it could still fly so we couldn’t catch it to investigate further. We’ll keep an eye on him when we see him but he doesn’t have a nest so he isn’t tied to his territory very tightly and we don’t see him very often. In Bastrop Bay just north of there, 38 & J0 have been incubating a set of eggs for 38 days now. Eggs typically hatch in 27 days so these are clearly not going to hatch. This pair has never had a chick in the four years of our study and I believe they are laying sterile eggs. This is one of two pairs in our study area that appears to have this problem. Both have been paired all four years of our study which is odd. Usually the female will find another male after a year or two of not fledging a chick.
This week for the first time ever, we noticed a pair chasing off their fully grown chick. Usually the chicks stay with the adults for 3-4 months after fledging and I have often wondered if the chick abandons the adults on its own or if the adults have to shoo it away. 12 & unbanded, the first pair to fledge a chick this year, were clearly shooing their chick XU away on Friday. The chick kept flying over to where they were and they would either chase it off or leave themselves and fly to a different part of the island. It was a bit hard to watch and I felt for the poor chick who has relied on the safety its parents for the last four months and now suddenly finds itself being shunned by them. It won’t be long before it will be the leader of the teenagers running wild out there though and I expect it will do just fine. Here’s a picture of XU when it was just a pup. It’s all grown up now!
We only found one new nest this week and it may be the last one of the year. Time will tell.
Current Stats: 9 nests being incubated, 55 failed nests, 7 nests with unfledged chicks, 20 chicks fledged
Our grant from National Fish and Wildlife Foundation for this project requires a 1:1 match. If you would like to make a donation to help us meet our match goal, click on the donate now button and designate your donation to the oystercatchers. We appreciate your support!