Goldfinches, Barn Swallows, and hummingbirds
Answers to readers' questions about goldfinches that pluck daisy petals, swallows that help at the nest, and hummingbirds that appear to sleep during the day
Published: October 23, 2009
Goldfinches pluck the petals off my Gerbera daisies and let them drop. They do not bother the center of the flower. What can I spray on the flowers to stop the birds from destroying them? — Patricia Ipavec, Mequon, Wisconsin
Gerbera daisies are cultivars of one or more species native to South Africa. As members of the Asteraceae family, they are related to our popular native asters and sunflowers.
Goldfinches, as well as other small seed-eating birds, are fond of the mature seeds of the native flowers. The finches often take apart the flowerheads to pull out the seeds. I suspect this is what is happening to your Gerbera daisies.
Although you note that the birds do not bother the center of the flowers, there may be something about the structure or development of Gerbera daisies that deters them from continuing to that point. Since the finches are unlikely to be able to tell the difference between species of daisy-like flowers, perhaps they are attracted to the non-native Gerberas but unable to extract seeds from them.
Gerbera daisies are prone to infestation by small invertebrates such as spider mites, whiteflies, and aphids, which might be appealing food to goldfinches. Perhaps petal-plucking helps expose or dislodge the food items.
Other species of plants in the composite family, such as marigolds, have chemicals in the flowers that can act as insecticides. In my December 2006 column, I explained that this is likely the reason Common Grackles pluck marigold petals and preen with them - they are taking advantage of a chemical in the petals known to inhibit egg laying in some species of ticks and mites. I haven't found any research indicating that flowers in the genus Gerbera have similar chemical properties, and your birds don't appear to be using the petals in any way.
The birds have little or no sense of taste, so spraying something on the flowers won't help and could hurt them. I suggest planting Gerberas where the birds might be more reluctant to get on them (perhaps near the house or other high-traffic area). Or plant distractions such as native coneflowers close by, or put an upside-down thistle feeder in the yard. Readers, if you have more detailed observations of goldfinches or other species pulling apart Gerbera daisies, please pass them along.
At a Barn Swallow nest, I observed at least five individuals feeding three nestlings. Who were these extra helpers? — Bob Setzer, Rochester Hills, Michigan
Scientists use the term cooperative breeding to describe such scenes. Cooperative breeding tends to occur when territories or nesting places are limited, when resources are unpredictable, or when there is a shortage of suitable mates. In some cases, the helpers are related to the nestlings (often siblings from an earlier brood), but in other instances, they are unrelated non-breeding adults. For Barn Swallows, both situations have been reported.
Young Barn Swallows from a first brood have been known to provide the majority of feedings to the second brood. Sometimes, juveniles will also feed birds they are not related to, but the number of feedings is generally low and the reasons behind the behavior are unclear.
Adult swallows that help at the nests of unrelated birds usually don't provide a significant amount of food to the young, and the nests are not more successful in fledging young than nests without helpers. When a swallow cannot find a mate or nest site, it may assist at a nest in order to breed with or replace one of the mated pair. An extra male may even kill young nestlings to break up the mated pair and help himself to the female.
Do hummingbirds enter torpor during the day? I ask because I took a photo (right) of a Violet-bellied Hummingbird in Panama that appeared to be sleeping. The bird eventually flew off after many minutes in this position. — Neil Almond, Nanoose Bay, British Columbia
A few bird species, including some hummingbirds, do enter torpor. The state is characterized by a lowered body temperature and metabolic rate. It's usually employed at night to conserve energy in low ambient temperatures. (Founding Editor Eldon Greij wrote about torpor in his February 2006 and August 2009 "Amazing Birds" columns.)
Your hummingbird was sunning itself. Birds of all types will do this, often adopting weird postures for many minutes at a time. The behavior allows the warm rays of the sun to penetrate the erected feathers and heat the skin. This is thought to overheat ectoparasites and cause them either to drop off or to move around to somewhere on the feathers where the bird can then preen them off.