Our Nesting Census is this Saturday (June 5) from 7:30 a.m. to noon. Birders walk the trails of Mariton listening, looking and counting all of the birds that we can find. This is the 30th Nesting Bird Census held at Mariton.
People ask me how we know which birds are nesting. We don't for sure. But most birds have set up their nesting territories. So, any that we encounter along our set course are assumed to be nesting. Many of the birds are counted by recognizing their song. Because it is mostly males that sing, we are likely to undercount individuals.
Is that a bad thing? Not necessarily. We know that we are taking a four hour snapshot of bird life at Mariton in early June. I don't expect it to show the whole picture. We know that there are species nesting here that we don't often count during the morning. For instance we know that Screech Owls nest at Mariton, but we rarely count them during the period. We see Pileated Woodpeckers often, and know they nest here, but again we don't always find them during the count.
I can look at a photographs taken of the forest every year. I may not be able to discern each species in each photo, but I can learn a lot just by comparing one year to the next. Similarly, when I look over the Nesting Census records I can see how the forest has changed just by what species were being counted. I know that in the early 1980's there were more shrublands at Mariton, because they were seeing Brown Thrashers and Yellow Warblers. It wasn't until 1996 before we counted our first Pileated Woodpecker. They were probably nesting here before that, but I would be surprised if they were nesting in 1981 based on what other species were being counted then. So, while the Nesting Census isn't perfect, it does provide a lot of useful information easily.
