Circumstances: First found and reported by William Legge 10 November 2019 and seen again yesterday. A Tricolored Heron seen flying high over San Francisco yesterday evening may have been the same bird. This morning William Legge posted that the bird was back at Rodeo Lagoon. I arrived about 12:15 p.m. and met Calvin Lou who pointed out the bird which was hiding in reeds in the northeast section of the main lagoon. Fog made photography difficult, but I managed the photos above.
Description: A small dark heron with contrasting white belly. About the size of adjacent Snowy Egret, but with shorter legs and much longer bill. Dark slate color overall except for the white belly, chin and throat, and a couple of white head plumes. It also had loose lavender scapular plumes and a slightly crested appearance at times. Bill and legs were yellowish. Eyes reddish. Lores yellow. Foraged cautiously always within dense reeds. Caught one fish which it struggled to swallow while I watched.
Discussion: Appears to be an adult in non-breeding plumage. The only previous record of this species in Marin County was in 1996. California specimen records have been referred to the larger North and Middle American subspecies E. t. ruficollis characterized by a white neck stripe. The nominate race found in South America is smaller and has a darker neck stripe.
Digiscoped with Panasonic DMC-LX5 | Nikon FieldScope III | 30XWA | hand-held (no adapter).
References:
California Bird Records Committee [CBRC] (R. A. Hamilton, M. A. Patten, and R. A. Erickson, eds.). 2007. Rare Birds of California, Western Field Ornithologists, Camarillo, CA.
Frederick, P. C. (2013). Tricolored Heron (Egretta tricolor), version 2.0. In The Birds of North America (A. F. Poole, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bna.306
Hancock, J. & J.Kushlan. 1984. The Herons Handbook. Harper & Row, New York.
Martínez-Vilalta, A., Motis, A. & Kirwan, G.M. (2019). Tricolored Heron (Egretta tricolor). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/52689 on 13 November 2019).
Tricolored Heron (Egretta tricolor), In Neotropical Birds Online (T. S. Schulenberg, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. retrieved from Neotropical Birds Online: https://neotropical.birds.cornell.edu/Species-Account/nb/species/triher