Warblers Grounded by Rainy Weather

Nature Notes for October 2, 2015

As I write (on Tuesday, September 29), it is raining. A Nashville Warbler, a Tennessee Warbler and a Black-throated Green Warbler have taken refuge in my garden.

The weather was quite nasty on September 12 and 13. A cold rain was falling for most of the weekend, accompanied by a low cloud ceiling. Along the A.K. Sculthorpe Woodland Trail on Port Hope’s eastern waterfront, there was a grounding of small birds. A total of 24 species of wood warblers was seen over the weekend. The list included Tennessee Warbler, Orange-crowned Warbler, Nashville Warbler, Northern Parula, Yellow Warbler, Chestnut-sided Warbler, Magnolia Warbler, Cape May Warbler, Black-throated Blue Warbler, Yellow-rumped Warbler, Black-throated Green Warbler, Blackburnian Warbler, Pine Warbler, Palm Warbler, Bay-breasted Warbler, Blackpoll Warbler, Black-and-white Warbler, American Redstart, Ovenbird, Northern Waterthrush, Mourning Warbler, Common Yellowthroat, Wilson’s Warbler, and Canada Warbler. This is about all the expected warbler species for this time of year. 

 Wilson's Warbler

Blackburnian Warbler

 Magnolia Warbler

A small sample of the many warblers grounded recently in Port Hope

Photos © Rob Lonsberry Photography

This grounding consisted of hundreds of birds in this small area. The warblers were accompanied by several Red-eyed Vireos and Swainson’s Thrushes, as well as a single Gray-cheeked Thrush and a Veery. The first of the migrant sparrows was also present: Song Sparrow, Lincoln’s Sparrow, Swamp Sparrow and White-throated Sparrow. Several species of flycatchers were also included in the flocks of birds: Eastern Wood-pewee, Yellow-bellied Flycatcher, Least Flycatcher and Great Crested Flycatcher.

In rainy, stormy weather, small migrants are forced to land. In good weather, the birds would just keep going and many fewer would be seen on the ground.

They weren’t easy to spot. Small birds are very good at hiding behind leaves and branches. The smallest of the warblers weigh only about 8 grams. Observers also had to contend with raindrops fogging up optical gear and eye glasses, and dripping off the brims of hats.

Most small land birds migrate at night. It is thought that the darkness provides them some protection from hawks, which migrate by day. Winds tend to be calmer at night, so the birds don’t have to expend as much energy to fly. As well, they may navigate by the stars.

These little birds are on a long journey. Most have come from breeding grounds in the boreal forest of northern Canada and are travelling to Caribbean islands, Mexico, Central America or South America. It is difficult for humans to believe these long trips, without benefit of an airplane or the use of GPS units. The trip is fuelled only by millions of tiny insects, berries and seeds.

The fall migration takes place over a more protracted time period than that in the spring. There is not the same pressure to arrive at the breeding area and raise a family. As long as the birds have adequate food, they can take their time.

Most land birds start south in August, beginning with insect eating birds such as warblers and flycatchers. There is a big movement of warblers in late August and through September, while the latest migrant warbler, the Yellow-rumped Warbler, may be around until almost the end of October.

Seed-eating birds such as sparrows and finches usually begin their migration somewhat later. Most sparrows begin migrating in late September, but the peak of their passage is in mid-October.

Birding in the rain, although it may be miserable for the observers, can be quite exciting.