It is exciting every year to see the transition from winter to spring reflected in the bird population. April was particularly well reported with many birders out in the field looking for returning and unusual migrants. Some of the best days for birding occur when spring snowstorms arrive, forcing migrating birds to the ground to wait out the storm. There were numerous reports from the snowstorm in the middle of April (April 16 and 17) of both common and unusual species. It was also noticeable how the birds changed on a daily basis with 105 White-faced Ibis at Boulder Reservoir one day, and only a single ibis left the following day. There were two well documented reports of Glossy Ibis among the many White-faced Ibis in the county. These are notoriously difficult species to differentiate, as are Rusty Blackbird and Brewer’s Blackbird in breeding plumage. However, the general consensus seems to have been that there was a Rusty Blackbird at Boulder Reservoir.

The most unusual species reported was a Black Phoebe at Walden Ponds. This is only the second report for the wildlife inventory since it started in 1979; the previous sighting was in 1988 over twenty years ago. Unfortunately, it did not linger although many birders looked for it. One rarity brought in by the spring snowstorm of April 16 and 17 was a female Vermilion Flycatcher at Walden Ponds which several birders managed to see. This is the fourth report of Vermilion Flycatcher for the wildlife inventory. Interestingly, the previous reports have been in May, June and December so there seems to be no consistency as to the best time to look for this unusual species. A Sage Sparrow, also found at Walden Ponds, was the first seen since 2005. Other less usual sightings included Chukar (last seen in 2007), White-winged Dove and Short-eared Owl.

Shorebird migration was well underway in the second half of April and nearly all our regularly occurring species were reported. Good sightings included Semipalmated Plover, Black-necked Stilt, Whimbrel, Long-billed Curlew, Semipalmated Sandpiper and Western Sandpiper. Seven gull species were reported over the two months with Mew Gull being seen both months. Duck numbers steadily declined as most of our resident winter ducks migrated north for the summer; the most unusual sighting was the continued presence of two White-winged Scoters on Baseline Reservoir. Warbler migration was only just getting started at the end of April but unusual sightings included Northern Parula, two Black-throated Gray Warblers and a Black-and-White Warbler. Solitary Vireo was reported in March and Cassin’s Vireo in April. Sightings of Cassin’s Vireo seem to be equally split between spring and fall migration; there have been significantly more sightings of Cassin’s Vireo than there have of Blue-headed Vireo since the species were split over a decade ago. However, both these vireos were seen more than a month earlier than previous spring sightings.

In summary, March was a very poorly reported month with only 96 bird species observed. However, April made up for this by having 164 species, which is above average even if it does not rival last year’s record high of 179 species. The number of species was not helped by a lack of reporting of common species such as White-throated Swift, American Dipper and Brewer’s Blackbird. TOP