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Occasional posts - from the quirky to the momentous - on the life and times of the Methow Conservancy.
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Thursday, March 17, 2016

Corvid Course - Class #6 Clark's Nutcrackers, Memory & Whitebark Pines

Our 2016 "Conservation Course" started January 25th.  Below are short-hand notes taken by Raechel Youngberg and a video by CJ Peterson, both class participants.  See notes and videos from the previous classes here:
first class
second class 
third class
fourth class 
fifth class

Class #6 - Clark's Nutcrackers, Memory and Whitebark Pines with Teresa Lorenz & Eireann Pederson
February 29, 2016 

 Watch and listen to the entire class on this video
Clark's nutcracker in Mazama eating suet, by Mary Kiesau
Clark's nutcrackers are named after William Clark of the Lewis and Clark expedition. Clark's nutcrackers are social animals that straddle two worlds. In one world they are similar to other corvids in that they eat a diverse variety of foods but in the other world they are specialists who primarily dine on large pine seeds. They are partial migratory birds, meaning that specific groups migrate to different areas but there still may be Clark's nutcrackers in your backyard year around however they are unlikely to be the same Clark's year around. 

They are gray-bodied birds with black and white wings and tails.  The juveniles have a light gray face and a pink mouth. It is impossible to tell male and female apart based on coloration but it may be possible to do so by observing their behavior. Clark's nutcrackers look similar to northern shrikes, and gray jays.

By Michael Sulis,
Clark's nutcrackers have a large brain for their body size and a large hippocampus, which is one of the main areas of the brain for memory. They have the best spatial memory of any other animal in the world. Clark's store 50-80,000 seeds in caches across a wide area every year. A nutcracker can hold up to 80 whitebark pine seeds at a time in the sublingual pouch inside their mouth, and then carry these seeds for 20 miles before caching them. Clark's can carry up to 20% of their body weight in seeds. During the fall Clark's nutcrackers primarily eat only "stone pine" seeds, preferably whitebark pine, but during the rest of the year they are opportunistic foragers. (Stone Pines are pines that are distinguished by large, dense seeds that lack wings and therefore depend upon birds and squirrels for dispersal across the landscape.  There are five species worldwide.)

Pine trees produce variable seed amounts each year. Some years there is a bumper crop and Clark's nutcrackers will have plenty of seeds to go around but other years seeds are scare and they rely more on other varieties of food. Clark's have been known to eat salamanders, eggs, small birds and frogs. But their primary food besides pine seeds is insects. 

Whitebark pine in the Okanogan NF
Whitebark pine (Pinus albicaulis) was discovered by George Englemann in 1863.  They are the only stone pine (tight closed cone) tree in the Americas. They have large seeds with a high fat content. They rely on animals such as Clark's nutcrackers to distribute them. However Clark's nutcrackers in the Pacific Northwest often prefer to cache seeds in trees rather than in suitable areas for white bark pine to grow, because they need to be able to find them in the winter when snow levels are high.  

Whitebark pine are the 11th longest living tree species on the planet. The oldest whitebark pine was 1,270 years old and nearly a foot in diameter. 

Whitebark pine are high elevation trees (6000-7000ft) and can be identified by their five needles. Whitebark pine's habitat range, not so coincidentally, overlaps with the range of Clark's nutcrackers. 

Whitebark pine cone (Wikimedia)
Whitebark pine take 20-30 years to reach cone bearing age. They then must mature to 60-80 years of age before they produce a large cone crop. It takes two years for a cone to reach maturity, and a whitebark pine will take 3-5 years between cone cycles.   So, it's a slowly regenerating tree.

Whitebark pine are Clark's nutcrackers preferred food. While Clark's nutcrackers are able to adapt to different food sources, whitebark pines are not as adaptable. Whitebark pines are early colonizers after disturbance, and the fire suppression of the west has allowed other trees such as lodgepole pine and other shade tolerant species to easily out-compete them. Whitebark pine also face threats from blister rust (fungal disease that was introduced from Europe), mountain pine beetles, and climate change. 

Whitebark pine was proposed to be listed under the Environmental Species Act (ESA) multiple times. However due to the decrease in the mountain pine beetle population, the whitebark pine was removed from the proposed listing on 12-24-15. Whitebark pine is currently listed as endangered in Canada.

Wednesday, March 9, 2016

Corvid Course - Class #5 The Study of Crows

Our 2016 "Conservation Course" started January 25th.  Below are short-hand notes taken by Raechel Youngberg and a video by CJ Peterson, both class participants.  See notes and videos from the previous classes here:
first class
second class 
third class
fourth class

Class #5 - The Study of Crows with Kaeli Swift & Loma Pendergraft
February 22, 2016 

 Watch and listen to the entire class on this video

Crows, as we have discussed in previous classes, are socially monogamous but can have multiple sexual partners. Crows form a tight pair bond that generally lasts for life. The average crow lifespan in the wild is 15-17 years but captive crows have been documented to live up to 30 years of age.

Crows take part in a unique rearing style called cooperative breeding. A mated pair may be assisted in raising a chick by a previous son/daughter or sometimes an unrelated crow. This breeding style has not been proven to assist the mated pair that much but studies have shown that it is beneficial during low resource years.

Crows are social animals and commonly roost together. This practice is called communal roosting. Seattle area crows have been documented to roost together at UW-Bothell campus. Scientists have some theories as to why this practice may occur. One theory is that roosting together protects individuals from predation by cats, red-tailed hawks and coopers hawks. Scientists also believe that crows may exchange information with each other at these roost sites.
As discussed in prior classes crows are highly intelligent animals and have a well-documented use of tools. The New Caledonia Crow has been documented to make two types of tools. Crows display the following attributes of intelligence: causal reasoning, flexibility, imagination and prosecution.

While crows excel at intelligence tests that demonstrate cause and effect knowledge, one study showed that crows struggle with counter-intuitive tests that require inference.

Crows are one of twenty-five species to have been documented demonstrating play behavior. Scientists once thought that animals played to prepare themselves for survival in the wild. However a recent study took one group of animals that did not play during development and measured their fitness against a group of animals that did play during development. There were no significant changes between the two groups. Play during development is now thought to help animals cope with stress better throughout their life. 

The Avian Conservation Lab run by John Marzluff at University of
John Marzluff with a crow
Washington has been trapping and banding crows since 1997.  In one study, researchers wear a caveman mask and hat while trapping the crows. The researchers then test the bird’s reaction to the caveman mask, a "neutral" Dick Cheney mask, the hat without the caveman mask, and an unmasked participant. When crows that have been trapped are exposed to the caveman mask they participate in scolding and mobbing behaviors towards the researcher. Mobbing is when groups of crows attack or harass a potential predator. Scolding behavior refers to a specific call the crows make when they feel threatened.

Additional studies by the Marzluff Lab have demonstrated that crows can recognize faces that have fed them or that have hurt them in the past. Crows do not seem to forget this knowledge and they pass this information onto other crows, including their young. The Marzluff Lab researchers have been mobbed and scolded by more crows than their study has caught. A sign that captured crows are teaching other crows that the caveman mask and hat combination signifies a potential threat.  

Crows mobbing a red-tailed hawk
Mobbing is costly and can be dangerous for the crow. Crows only use this tactic when they deem the predator worth the risk. One study sought to learn more about this behavior. An osprey is as big as a hawk but it eats fish so it poses little to no risk to crows. Crows rarely mob osprey - however in areas where encounters between osprey and crows are uncommon (crows don't know what osprey are) the rate that crows mob osprey is higher. In areas where osprey and crow encounter are common mobbing rates are lower. When crows do mob osprey it is generally the younger naive crows that do so. The older experienced crows recognize that an osprey poses no threat and will not participate in mobbing events against osprey. This is yet another example of crows using mobbing events to teach potential threats to younger or naive crows.

One study sought to find out if crows felt threatened by a researchers gaze (eye contact) or their expression. Studies were conducted to see how close a researcher could get while either staring at the crow or making an expression. Then an observer would note how close the researcher got before the crow reacted (flew off, looked at the person etc). The study found that crows flew away more often when a researcher was walking towards the animal while staring at it. Eye contact is considered a threat because it is a sign of potential predation whereas facial expressions can be faked and are not reliable.