Thom Smith: Dragonflies and some birds can be territorial
Q: As I watch the dragonflies patrolling my backyard and the swallows swooping over my fields -- both on a quest for insects -- I wonder: Do either of the two species have "territories" that they defend like [other] birds and some other animals? Also, one of my neighbors has a large field he mows for hay. I know bobolinks return there every year to nest and I look forward to seeing/hearing them. My concern is he may be possibly mowing it too soon, when they are still nesting and raising young. The birds seem to arrive sometime in late-to-mid April. This year, the area where they nest was mowed in mid-to-late June. What would the consequence be to the bobolinks if he is mowing too soon for them to finish nesting and raising their young?
A: I have never noticed dragonflies being territorial in the field, and to meet deadline, I searched for "dragonfly territory" on Google rather than attempting to contact an entomologist friend. I read that males especially, "are usually territorial and defend their turf aggressively." In addition, competition for females is sometimes violent; males will fiercely drive off other male suitors. Tree swallows are also territorial, and arrive before females to locate and lay claim to nest cavities, either natural or man-made. This has to be accomplished upon arrival as soon as possi ble to beat potential competitors, especially other male tree swallows. Several cavity nesters -- including bluebirds, house wrens, black-capped chickadees and English sparrows -- will compete. I watch the hubbub in our backyard each spring as several male swallows, bluebirds and English sparrows argue over possession of the two boxes I have erected. Last year, the bluebirds got one box, and I believe the English sparrows in a neighboring box destroyed the eggs and chased the parents off. This year the bluebirds were successful and the day following their five hatchlings leaving the nest, tree swallows took over and are now feeding their young. As soon as nesting is over, tree swallows lose their territorial instinct and begin their fall molt while gathering in ever larger flocks to migrate.
Bobolinks arrive about the beginning of May, usually around May 5, and have decreased in recent years. The fewer successful nests result in fewer birds and is due in part to loss of habitat (building of homes where prime hay fields were once maintained) and the planting of early grasses that are harvest-able earlier than our native warm-season grasses. Earlier cutting destroys nests and eggs or nestlings. The advantage to the farmer is that it allows for additional cutting, up to three in a season.
Just today, I heard bobolinks singing in a Richmond hay field, and by mid-July they will be quiet and a week later will be seen perched on tall grasses and flowers as they gather in flocks for their fall migration to winter in the South. To answer your question, mowing fields with known bobolink nests should be postponed until mid-July. This is often financially impossible for local farmers.
Abandoned fields are not suitable nesting sites for this attractive blackbird either. Hay fields left alone will be used lessfrequently, until not at all, possibly because of accumulation of dead grass and weed litter and encroachment of trees.
Q: [We are] renting a home in Dalton for the summer and I have seen what I think is a robin with a partially colored white head and body. This is the size of a robin and is always seen with a "normal" robin. What is it?
A: Simply put, it is a robin, a partially albino robin. The Berkshire Museum has a fully albino specimen with pink eyes in its storage collection, and through the years I have had numerous reports of other albino and partially albino birds, including other robins.
Questions and comments for Thom Smith: Email Naturewatch@live.com
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