ML259013821

Age

Not specified

Sex

Not specified

Observation details

Accepted by the CBRC, record number 2020-080. [Update entry to RTHU based on input from Sheri Williamson on 9/1: "It's a juvenile male Ruby-throated. The mask is darker than usual in juvenile male Black-chinneds, and the tail notch is quite deep, exposing the black tips of R3-4, and the third photo shows the diagnostic elongated oval tip on P5 and the sharply pointed P6."] This appears to be either a Black-chinned or Ruby-throated Hummingbird, the two species in the genus Archilochus. BCHU is rare for this location. RTHU is very rare for the state of California with no accepted records in Alameda County. I believe the totality of the field marks point to RTHU, but am entering as BCHU/RTHU as I seek out further opinions and research further. I first noted the presence of a hummingbird that seemed smaller than the expected Anna’s near a flowering shrub in the wooded area of Cesar Chavez park. After some 15 minutes a hummingbird appeared that seemed different to the naked eye with a sort of white collar extending above the shoulder. It landed and I took some images. The bird was silent. It then flew off and was not seen again for the following 20 minutes. From the images I note dark, contrasting auriculars, a white spot limited to just behind the eye, green back with golden hues, greyish crown, forked tail with white tips to the rectrices, lightly marked white throat, stout straight-ish, medium length bill. Some of these characters are good for a female type Black-chinned Hummingbird, whereas all of them support Ruby-throated Hummingbird, and, in the aggregate, are not good for the other likely hummingbirds for the area. I will go through and attempt to eliminate the non-Archilochus hummingbirds in order of likelihood. In all cases I am considering female/juvenile of the species: Anna’s Hummingbird - By far the most likely hummingbird species in this location, and anywhere in the county at this time of the year, is ANHU. The bird in question had a forked tail when at rest. This is not noted in ANHU and this feature alone can rule out ANHU. However, there are other marks against ANHU: The post-ocular white is limited to the area behind the eye - In ANHU the white should wrap over the top of the eye; buff color on flanks and around legs - ANHU lacks buff coloration; the throat is white with light marking - an adult female ANHU typically shows a dark spot in the throat area. Juvenile ANHU typically has an unmarked throat, but a juvenile ANHU would not likely have a bill as stout and long as this bird. I believe the totality of these marks safely rules out ANHU. Rufous/Allen's Hummingbird - The bird in question lacks rufous and cannot be RUHU or ALHU. Costa’s Hummingbird - The stoutness and length of the bill, and darkness of the auriculars can rule out Costa’s, among other features noted in the ANHU section above. Calliope Hummingbird - Lack of extensive buffiness in sides of chest as well as stoutness and length of bill rule out Calliope. Black-chinned Hummingbird - The auriculars are dark, prominent and very contrasty. In BCHU the auriculars tend grayer, less prominent, less contrasty. These dark auriculars would be unusual in BCHU. The forehead appears grayish, a mark in favor of BCHU, but does not rule out RTHU. The wingtips appear to not reach the tip of the tail as expected in BCHU. The wingtips do not appear to show a broadening or curving at the tips as expected in BCHU. The bill is of medium length and in some angles has a slight curve to it. It is perhaps not conclusive in separating BCHU and RTHU, but the bill seems typical for RTHU and does not seem typical of BCHU, which, if adult, should be longer and more distinctly down-curved.

Technical information

Original file size

1.32 MB