By Susan Heath
I jumped the gun a little by posting my last entry mid-week before we were done with week two. What can happen in two more days in the field? A lot it turns out. We go to West Galveston Bay on Mondays and Fridays and Bastrop and Drum Bays on Thursdays to accommodate our UHCL graduate student Amanda Anderson’s class schedule. So on Thursday we headed out to Bastrop Bay. There are three pairs of oystercatchers that nest here. We saw one of the pairs on a reef at the mouth of Bastrop Bayou so they clearly don’t have a nest yet. On another reef was a bird we banded as a chick last year in Swan Lake just north of the I-45 bridge to Galveston. Oystercatchers don’t breed until they are at least three years old and the wanderings of the young birds that aren’t old enough to breed yet is somewhat of a mystery. We saw this particular bird the previous week as well so it appears it likes this area and doesn’t mind being a loner.
Out in the bay we didn’t find any oystercatchers until we were about ready to leave when one of the pairs came flying in calling to us and landed nearby. J0 and 38 have been paired since the beginning of our study and they nest on an island in Bastrop Bay that has a skimmer colony as well as a cabin that appears to only be inhabited on holiday weekends. It is never apparent how the oystercatchers know when we are around but if they are in the area and they hear the boat, they come flying in. I have seen adult pairs completely ignore the numerous fishing boats that pass by them daily but come flying in from long distances when we approach. They know us and they don’t really like us. I try to reassure them that we are trying to help them by learning everything we can about their needs but it doesn’t seem to help much. It’s clear we aren’t their best friends by a long stretch.
In Drum Bay there are seven pairs of oystercatchers that nest. Last year we had some drama when three females disappeared. We found one of them dead but the other two simply disappeared. It wasn’t clear what happened but there had been a storm a few days prior so that might have had something to do with their disappearance. This caused a major shift of the pair structure in this bay since the females are always on the lookout for a male with a better territory than the male they are currently paired with. The type of system is called female choice because the males maintain the territories and the females find a male with a territory they like. Anyway, one of the pairs there was unbanded so we tried to trap them but only got one. Here’s Amanda holding the newly named CH. I think CH is a male based on size but the measurements were intermediate and since we didn’t catch them both so we could compare their sizes, the official sex will have to go as unknown.
On Friday we headed out to my favorite field site – West Galveston Bay. There are between 40 and 50 pairs of oystercatchers that nest in this area. The three nests that we found previously were all being incubated so no problems there. We went to check on another pair near the Fat Boy’s boat ramp that nested early last year and sure enough we found that R3 & R4 had a nest with two eggs! They didn’t appear to be incubating them yet so they will probably lay one more. Last year we put out signs on nesting islands to warn people that there are nesting birds so they will know to stay away. One of the signs on this island was broken so we replaced it.
I thought that was the end of the early nesters but I was wrong. Amanda noticed another pair hanging out where they usually have their nest rather than out on the reef feeding and when we checked we found they had a nest with three eggs. Go J6 and P4! This pair nests on a tiny scrap of an island close to Tiki Island. If they get a late start, their nest is doomed to overwash so they are smart to start early.
And then on South Deer island where there are eight pairs of oystercatchers we found yet another nest, this one belonging to JN and JE. This pair’s nesting territory is right in the middle of a huge Laughing Gull nesting area so for them an early start is critical for success. Right now there are no Laughing Gulls there so their eggs are safe for the time being. In another month it will be a different story.
Six nests in February is unprecedented and there’s still another week to go. I’m not sure if we are finding more because we know how to search more effectively now or because more birds are nesting early. Whatever the reason though, all the pairs that have nests are in places where there are specific reasons why starting early is good. These birds are smart!
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