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Sunday, January 31, 2016

Corvid Course - Class #1 Intro to Corvids

Our 2016 "Conservation Course" started January 25th with an introductory class by David Moskowitz.  Below are notes taken by Raechel Youngberg and a video by CJ Peterson, both class participants. 

Class #1 - What Makes a Corvid a Corvid?

 Watch and listen to the entire class on this video

Corvids originated from the Australia/New Zealand region around 17 million years ago. Corvids belong to the Passerine or perching bird order. There are currently 23 genera and 120 species across the globe. Corvids are a very successful family and have colonized most of the earth. Corvidae include crows, ravens, jays, rooks, jackdaws, magpies, treepies, choughs, and nutcrackers.

There are very few endangered corvid species. One species of note, the Hawaiian Crow, is extinct in the wild and has dwindling numbers in captivity. A number of factors led to the demise of the Hawaiian crow such as disease, predators, and loss of habitat.

The Corvidae family is often described as intelligent, adaptable and playful. They have a brain to body mass ratio almost equal to that of the great apes and whales. Certain species have been documented using mirrors, which is a sign of self-awareness. There is well documented tool usage by certain species such as ravens and crows (See a video here).

Ecologically, corvid relationships with other animals, particularly predator-type carnivores, has a very long history.  It's even thought that ravens have had an evolutionary impact on wolf socialization and group formation.  Ravens can account for 40% of scavengers on wolf kills which led wolves over time to hunt in packs so they consume their kills faster and keep the food within their family.  Corvids frequently consume kills made by other animals.

Basic Morphology:
-Most are medium to large in size
-Blue, black, iridescent in color
-Racous call
-Stout bill
-Bristle-like feathers on base of bill (unique to corvids)

-big eye sockets
-stout bills
-relatively large brain case

-Stout bills are flexible in how they are used (generally not specific to certain types of food, opportunistic feeders)
-Insects make up a large part of their diet

-Elliptical and flexible wing shape
-Not the quickest wing shape but highly adaptable

Track drawings by David Moskowitz
-Digitigrade animals (walk on toes)
-Versatile movement (for crows/ravens) can walk, hop, jump on the ground
-A foot track on the grade shows that the middle toe hugs the inside toe (specific to corvids)

Many birds produce "cough pellets," something many of us know owls to do, but corvids do as well.  Pellets are the indigestible material a bird consumes that they then regurgitate. Owls stomach acids are unable to digest bones so you often find bones and fur in their pellets. Hawks are able to digest most bones and so you do not find such materials in their pellets. Corvid pellets consist of quite a bit of insect casings among other materials.

-Territorial (depends on species, ex: ravens seem to be more territorial than crows)
-Many species are socially monogamous but sexually exploratory
-Nests vary depending on species but are fairly loosely constructed of sticks and branches, and reflect the size of the animal.
-They spend a fair amount of time rearing young compared to other families of birds

Our Western Corvids (Page numbers are for The Sibley Guide to Birds)
Ravens communicating about a fish by David Moskowitz
Common Raven: Corvus corax (pp 359)
-thick bill
-spade/wedge tail
-often soar
-usually found in pairs (sometimes you see more when there is food nearby)
-more territorial

American Crow: Corvus brachyrhynchos (pp 360)
-cut/straight tail
-never soar
-hang in groups

Northwest Crow: corvus caurihus (pp 360)
-Found on coastal areas in Washington and BC.

Black Billed Magpie: Pica hudsonia (pp 358)
-Distinct coloration
-Long tail
-Associated with open landscapes
Steller's Jay by Mary Kiesau

Steller's Jay: Cyanocitta stelleri (pp 357)
-Often misidentified as blue jays
-brilliant blue coloration
-Associated with forested landscapes

Scrub Jay: Aphelocoma californica (pp 352)
-Arid environments
-Associated w/ oak trees
-missing crest on head
-lighter bellies

Pinyon Jay: Gymnorhinus cyanocephalus (pp 356)
Gray Jay by Mary Kiesau
-Associated with pinyon pine and juniper forests
-easily confused with scrub jays

Gray Jays/Whiskey Jack/Canada Jay (Camp Robbers): Perisoreus candadenis (pp 356)
-Very curious about humans
-Found in subalpine ecosystems

Clarks Nutcracker: Nucifraga columbiana (pp 356)
-Smaller than crows but bigger than jays
-Primarily eat whitebark pines nuts but will eat other pine nuts such as our ponderosa pine