May is always the most exciting month of the year with a high chance of seeing migrating rarities. The number of species seen does not always reflect the number of rarities as it is influenced by other factors such as a late shorebird migration, a strong warbler migration, the lingering of some winter species and the reporting and observation of all the standard common species. The 218 bird species seen in May 2011 was a respectable total but was still a long way off the record of 243 bird species seen in 2002. Alder Flycatcher was reported for the first time since the wildlife inventory started in 1979. This is one of the notoriously difficult to identify Empidonax flycatchers; the safest way to separate it from our more common Willow Flycatcher is by voice. Other unusual flycatchers included Ash-throated Flycatcher, Eastern Phoebe and Cassin's Kingbird. Both Least Flycatcher and Gray Flycatcher were seen in small numbers and appear to be on the increase.

Shorebird migration was definitely trailing off although Whimbrel, Semipalmated Sandpiper and Baird's Sandpiper, all seen in the first week of May, were new additions for the year. Two Red-necked Phalarope were seen at Walden Ponds later in the month. Two Caspian Terns at Walden ponds delighted many observers. Three Red-headed Woodpeckers observed in different locations was a significant showing for this increasingly rare species. Mississippi Kite was reported for the third time since the wildlife inventory began– this is a species that is spreading from southern Colorado and we can probably expect to see further reports. A Cassin's Sparrow was reported at the end of May and another Black-throated Sparrow was seen in addition to the one sighted in April. A Carolina Wren continued to linger in south Boulder. White-eyed Vireo, McCown's Longspur, Summer Tanager and Baltimore Oriole were all less usual species.

Warbler migration was strong continuing the trend started at the end of April. Less usual species seen in May included four Tennessee Warblers, a Northern Parula, a Chestnut-sided Warbler, three Black-throated Gray Warblers, a Blackburnian Warbler, two Palm Warblers, five Blackpoll Warblers, a Black-and-White Warbler, three American Redstarts, an Ovenbird, three Northern Waterthrushes and two Hooded Warblers. Perhaps the most notable feature was how many unusual individuals were seen in all regions of the county. TOP