Friday, April 1, 2011

March 25-April 1 - Spring Migration Monitoring

Spring Migration Monitoring has begun and we are excited to be outside every day experiencing spring migration. This is our pilot spring season, and with no other observatories in British Columbia conducting a spring monitoring program, this makes our program especially unique and informative.

As noted in our previous entry the first few spring migrants arrived at the end of the our Winter Songbird Monitoring program. By the time our spring program began on March 25th, plenty more migrants and breeding birds had arrived. Every morning we are now serenaded with the sounds of bird songs, heralding the arrival spring. Not to be outdone the local population of Pacific Chorus Frogs are now beginning to call in earnest as well. The weather, as to be expected at this time of year, has not always cooperated with our banding efforts and we have not been able to band every day. But rain or shine our daily census walk has also been able to track the arrival of spring, especially for species that usually avoid our nets.

Flocks of both Tree and Violet-green Swallows have been seen daily, with 160 Violet-green Swallows on April 1st the largest to date. Hummingbirds have been absent since their first arrival on the 17th, but a Rufous Hummingbird was observed on the 1st. Our most notable catch so far this season has been a Northern Saw-whet Owl. There are no records for Iona Island in the spring, and only four in total for the area, so this bird was truly a surprize.

Many people this winter have watched and photographed a adult Northern Shrike around Iona Island, principally in the area west of the outer ponds. This bird has not been seen for at least a week or two now, but a new second-year bird has replaced it. The bird had tempted us for a few days, flying near our nets and even getting out of one once. But on the 29th it was banded and it has remained in the area since then.

One sure sign of spring has been the arrival of Yellow-rumped Warblers. The wintering population of Myrtle and at least one hybrid Yellow-rumped Warblers have been augmented with at least 5-10 newly arrived Audubon's Warblers. Myrtle and Audubon's Warblers are fairly easy to tell apart, with the most obvious field marks being a white throat and supercilium in the Myrtle and yellow throat and no supercilium in the Audubon's. Hybrids between the two can vary in their plumage, but are usually typified by some yellow in the throat and an indistinct whitish supercilium. The photos below illustrate Audubon's, hybrid and Myrtle Warblers.

Most of the other newly arrived birds have been Lincoln's and Song Sparrows. Only a few of the former have been noted so far, with the first on March 29th. Song Sparrows have really begun passing through with many, mostly males, seen and heard on a daily basis. The first American Goldfinches were noted on March 30th, and increasing numbers of Brown-headed Cowbirds and Brewer's Blackbirds have also been seen. At least one Western Meadowlark is still around and was seen on the 1st.

Orange-crowned Warblers and White-crowned Sparrows have begun arriving in Oregon, it will now only be a few more days before we will begin seeing them here. Spring is here and it will be exciting to see what birds will arrive over the next week!

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