A Common Raven (Corvus corax) Roost
I spent the evening of February 19, 2001 in the middle of perhaps 1000 Common Ravens! This was certainly one of my all-time birding and recording highs!
The birds started arriving at the roost near Sedona, Arizona at about 5:50 pm, and they continued to filter in over the next hour or so. Sometimes the sky was so full of Ravens that I could not count them. By the time they were settled in, Becky and I estimated that there could be as many as 1000 in the roost. They came from all around, but mostly from the west and southwest - sometimes in groups of 10-12, sometimes singly, and very often in pairs. They alighted in the tops of the juniper and Arizona Cypress trees around us and spent the next half-hour or so rearranging themselves - flying from tree to tree and chattering incessantly the entire time. Each Raven had a distinct voice, and it was easy to see that they could recognize each other by voice.
It seemed as though a bird would alight in one tree with several others, have a "conversation" with those birds, then leave to "visit" with another group - much like what a clan of humans might do when returning to the village from a day's hunting. Finally they all settled down and each bird moved into the interior of the tree - near the trunk, so that, by the time they were finished there were no birds in sight!
The cacophony that accompanied this ritual was astounding! The range of vocalizations was immense, complex, and unique (in my experience) to the roosting environment. That is, I have never heard many of these vocalizations outside the roost.
The entire process (and it is a complex process) took more than an hour and it was high-energy all the way!
Feb. 19-March 8, 2001 - I have visited the roost many times in the evning and during the day. The evening ritual is similar each night - birds arrive at the "staging areas" outside the roost, seemingly to socialize, then filter in to roost just 30 minutes before dark. At the staging areas they engage in fancy flying (acrobatics, skimming through the trees at top speed, high-speed chases, etc.) and a lot of what appears to be play. Sometimes one will pick up a stick and others play "tug-of-war" with him, some turn over rocks apparently searching for insects or other invertebrates and occasionally swallowing something they find, one carries a large (18", 50 cm) stick in his feet as he flies and others chase. At the roost itself, there is much shuffling about of the inhabitants - some fly to one perch and remain there until darkness. Many others land in one spot and soon fly off to another with no apparent provocation or purpose. Often a bird will land in a tree already occupied by others and cause turmoil - the birds there may object to the new arrival, and even physically prod and gently "attack" him until he leacves - this is accompanied by much of the whining and mewing heard at the roost.
Single birds, usually at the tops of trees, croak loudly over and over and every vocalization imagineable is heard. Finally, as darkness envelopes the roost, they all settle down to sleep, heads retracted to rest on top of their shoulders, and quiet ensues. The silence is broken for brief periods by brief whining or cackling, but it finally settles to complete silence. I am reminded of a summer camp where the children have a hard time settling down for the night.
March 10, 2001 - I observed the birds at one of their "staging areas" about 1 km from the roost as they dealt with a road-killed cottontail rabbit placed on the rocks. I watched from a mile away. A few birds showed up about 90 minutes before sundown and sat in a snag a few meters from the rabbit. They watched the rabbit for 45 minutes before venturing closer to it. The first bird to inspect the bait more closely approached within a meter or so, then jumped back, as if the rabbit had suddenly moved. This was repeated several times befor that Raven left the area without touching the rabbit.
Within a few minutes another bird showed interest by approaching the rabbit repeatedly and jumping back, then finally reaching out to peck it quickly and jump. Finally this Raven took a tiny bite and jumped bak. Others observing this seemed to take this to mean that the rabbit was, indeed, dead and no threat to them. They gathered closer and closer, finally all feeding on the bait as the night closed in.
March 12, 2001 - The day has been drizzling and cold all day. The darkness arrived rather sooner than normal, due to the dense cloud cover. As the Ravens gathered in the roost, they are exceptionally quiet - all hunched down soaking wet in the wet trees.
March 14, 2001 - Roger Radd and I observed a road-killed Jack Rabbit placed in the same spot as the one on March 10th. The scenario was played out pretty much the same as before, except that this time, as 8 other birds watched the bait from a distance, a large male (identified by his heavy bill, ruffed neck and his "ears" which were held erect) strode up to the rabbit without hesitation and jumped up on it, picking bits of meat from its exposed back muscle. When the onlookers saw this, they gathered around the rabbit and tried to get some food, too, but they were repeatedly repulsed (gently) by the old male. His influence on the demeanor of the
waiting birds was immediate and remarkable. It was as if he had given them "permission" to come closer - as if his actions meant that this was, indeed, a source of food, not a threat. Curiously he soon left and the crowd of birds around the rabbit dispersed without feeding. A few minutes later another, smaller bird took a few bites and flew off. By this time the night had fallen and all of the attending birds (about a dozen) left for the roost without touching the rabbit.
March 17, 2001 - Today I thought I'd give my birds something that they are more familiar with to eat, so, these being birds from around the surrounding towns, I gave them a Big Mac and fries! At 5:45 pm, when the first birds showed up, I thoght they would see my offering and eat without hesitation. I was wrong! They treated the burger and fries exactly as they had the two dead rabbits - with extreme circumspection. It took 45 minutes before one would even approach the meal, and another several approaches/jumps back before one ate a fry. Only one bird partook, the others treated the foos as if it were on fire, and all left for the roost at dark without eating.
March 18, 2001, 7:00 am - I scoped the "burger site" from my observation area, about 1200' away, and saw that the burger patty and the buns had been eaten, but the fries remained! This lead me to believe that Ravens had eaten the patty and buns, since a coyote or javelina would have eaten everything. One lone Raven stayed to try for a fry. He approached/jumped back a few times, exhibiting a lot of "displacement" activity along the way - scraping the earth, flipping sticks out of his wway, etc., and finally grabbed a few fries and flew off several yards to consume them. He ate only a few, then flew off - no other birds visited this morning.
5:45 p.m. - The fries were gone when I returned this evening. The staging area filled up quickly, with birds arriving for their pre-roosting socialization. More pairs seem to be forming now, with a lot of "billing" and mutual "feeding" of sticks and pebbles, etc. I notice that one of their favorite passtimes is digging at the soft sandstone of the cliff, and turning over small stones, and then I see why. One Raven doing this finds a large scorpion and, instead of eating it, he tosses it down on top of another bird siitting on the cliff below him! The other Raven just flew off, without taking the scorpion (Ravens are commonly known to eat scorpions), and the finder also ignored his offering.
March 23, 2001 - I have been away from the roost for a few days recording in Buenos Aires NWR in southern Arizona, but the Ravens seem to have done fine without me! They returned to their roost on schedule, beginning 30 minutes or so before sundown and continuing to stream in (sometimes in groups of up to 25) until dark. One pair flew close "fingertip" formation (one bird slightly behind and to one side, wingtips overlapping) at top speed for 20 minutes - climbing, diving, tight turns and all around the sky over the roost until they seemed exhausted and flew down to the roost. They did not stay together at the roost. I am wondering if these are male/female pairs, or just two birds that enjoy the flight training? The groups that came in together were probably arriving en masse from one of the outlying staging areas.
March 24, 2001 - I placed two hen's eggs and a pound of ground turkey that Becky said had grown too old in the freezer on the butte, where I always place my offerings. The scenario was faithful, as the birds arrived. A few sat in the snag above the food and observed it for 35 minutes before any approached at all. Finally one began the approach/jump back procedure and, after 7-8 minutes of this, took a small bite and flew a few yards away to swallow it. He approached again and took another small bit and flew off. Other birds had, by this time, begun to gather around the bait - all of them staying 10-20 feet away, but watching the bolder bird closely. At some unseen signal they all lunged forward and started grabbing bits of turkey, then just as suddenly flew off to sit in the trees and rocks surrounding the area. It was as if the ground turkey had suddenly moved! These birds are obviously very nervous when feeding at something new like this.
I often observe that, as they approach bait slowly, they go through "diplacement activities" like digging small holes in the dirt, picking up and tossing sticks out of the way, or throwing pebbles aside.
By nightfall the crowd had grown bolder and a few took large chunks of the turkey and flew off, being chased by several of the others, as you would see Gulls do. One large bird finally sidled up to one of the hen's eggs and, taking the whole egg in his mouth, flew off a quarter-mile or so, chased by others. 15 minutes later another (or the same?) bird took the other egg and began to walk off, when he was gently attacked by another, and dropped the egg, breaking it. When the egg broke a "frenzy" ensued, with 4-5 birds suddenly getting into the action to consume the broken egg.
During all this we observed several instances of paired behavior - Becky noticed that a common "dance" was one in which one bird (the male?) puffed up his head and neck feathers into a large "turban" and bowed gracefully and slightly while spreading his wings and tail just a bit. They also bobbed their head and touched bills frequently, played tug-of-war with sticks, etc. We also notice that they spend a certain amount of time picking up and swallowing small sandstone pebbles, about the size of peas or marbles. In their pellets under the roost I often see pellets comprised just of sandstone mud - I wonder if these pebbles are ground in the crop and regurgitated later as mud?
March 25, 2001 - Tonight we offered 2 eggs and some dry dogfood (kibble) - small bits the size of marbles. Only one bird took any dogfood and none touched the eggs.
The main body of birds at this staging area, though, were engaged in aerial acrobatics, as the wind direction was favorable to the updrafts at the buttes that they love to play in. They apparently like to play in the wind more than they like to eat! Several more pairs were observed to "dance" with the puffed head/neck and the gentle bow. More than 200 birds were playing at the buttes this evening in the wind before they left for the roost at late dusk. Their acrobatics took all forms - flat spins, where they spin around upright, as though they are on a turntable, hammerhead stalls (flying straight up until they run out of airspeed, then flipping over to dive head-first for the rocks again, chases, loops, "aileron rolls" (a complete roll along their longitudinal axis), and a lot of paired-flying when one bird flies momentarily upside down to reach out at the other with his feet. They are obviously having a ball!
April 7, 2001 - Today was a very windy, cold day. We spent some time in the afternoon examining the roosting area, tearing into various pellets regurgitated by the Ravens. I wanted to see if the rocks that we see them eating turn up in the pellets, and they do. Pellets consisting of grass seed husks are the most common. They seem to be pure seed,as if the bird "strips" the stalks of seeds by running his closed bill up the stalk - I'll have to watch for this behavior in the fields where they often sit. Inside these grass pellets there are often small (.5-2cm) pebbles, often as many as 10, and often all of one kind (one pellet may contain only small, white limestone pebbles or only small red, sandstone rocks). They seem to prefer the small limestone pebbles (are they buffering with them?). Lots of pellets are full of shredded plastic wrap, candy wrappers, aluminum foil, bits of broken glass, and other human trash. Some are comprised solely of rodent hair, with small bones mixed in. Occasionally we find "pellets" composed solely of stones, so they appear as a small pile of monotypic pebbles. Are the stones used as grinders? Here is a picture of a mixed composition pellet and this is one with plastic bits. Here is one composed primarily of hair. This one is a typical grass-husk pellet. These pellets are typically 3-6 cm long.
After looking at dozens of pellets we hiked up to the staging area and left them a small treat of chicken parts and raw fish scraps. They started appearing near the baits within minutes, while we were still only 100 meters or so away from the site. They appeared unfazed by our presence, so we sat down in plain sight of them, and observed. Because of the high (30 knots or so) winds, the birsd were more interested in playing than eating, though lots came by and hovered expertly in the wind to examine the offerings, none ate. But they did play! Their fancy flying was fancier than ever and we spend 45 minutes in the cold wind fascinated by their maneuvers. One bird carried a small stick, the size of a pencil, in his feet as he flew - he held the stick like a perch, so he appeared to be a bird on a trapeze without the wires! He tempted other birds around him to give chase, and when one got close to stealing his plaything (my interpretation, of course), he would transfer it to his beak for safekeeping, then back to his feet. Finally one of the others managed to dislodge the sticjk from his grasp and it fell to the ground. We left after freezing in the cold wind, but the Ravens never did feed, just examoined the food and flew off to play in the wind.
April 13, 2001 - I arrived at the roost's periphery at 630 - still plenty
of light and only a few roosters were there already. I sat very close to
the edge to observe the arrival of the birds. They filtered in as usual,
perhaps a few less than a month ago, but not markedly so. One bird came in
and sat at the edge in a small tree and played with an apple core. Another
arrived with a small stick in his bill, which he kept until he flew off to
find a new perch. There was the usual "begging", "king of the hill" playing
(?), etc. until 730 when it seemed that most of the birds had arrived and
the roost was starting to settle down.
In "king of the hill" one bird arrives and tries to usurp another's
position - usually the invader is repelled, but not always. Even if
successful, though, the usurper will usually leave the roost he just won
within a few minutes, and the constant churning of positions takes place
until nightfall. This churning of positions seems universal - I have not
seen a single bird who occupies the same roosting spot from the time he
arrives until he sleeps.
I did see several birds tonight that were missing feathers - one was
missing the entire tract of contour feathers under his right wing, others
were missing retrices, or a single primary. One had a bum leg that hung
down as he flew. I also got to watch one with "syringitis" - he croaked
hoarsely and softly for several minutes, seemingly unable to make any sound
louder than a whisper. Others "knocked" (which I feel is interpersonal
communication of some sort, "yelled" (which generally elicits a response
form another), croaked and whined. It occurs to me that I need to post a
"vocabulary" of sounds - so others can hear and standardize what a "croak"
or a "yell" or a "knock", etc. are - should they be synchronized with
Heinrich's vocal descriptions?
By 730 the last stragglers were filtering in slowly and the roost was
settling in, so I left.
April 15, 2001 - I went to the overlook to watch the butte staging area this evening. The birds had gathered there in force by 6:30. They were not kettling or playing in the wind, since there was no wind, so they had to satify themselves by tearing up piecs of fallen limbs, agave spikes, and the landscape in general. Several of them were moving and turning over rocks I thought were too heavy for them to lift, but they did it! I saw them grasp limbs as large as a two-by-four with their beaks and flip them over or move them easily aside. Some just tore up pieces of wood - looking for insects and other treats?
I saw one individual at the staging area with a real distinguishing characteristic - a pronounced hooked bill! His upper mandible was extended out and downward in the manner of a snail kite's - he was mature and seemed to be having no trouble using it, as he ripped apart an agave spike in expert fashion. It even seemed that he might have an advantage in doing this with that big hook - a nice beneficial mutation that could work it's way into the gene pool? The hook was thin, like a raptor's, and extended about 2 cm in front of and below his lower mandible. I'll call him "hook" from now on (how inventive!).
These guys all love to play with sticks - I saw them playing tug-of-war with sticks, offering sticks to each other, carrying sticks in their feet "trapeze" style, and chasing each other with sticks - maybe this is a juvenile (or adult) imitation of nest-building behavior. If juvenile play often imitates useful adult behavior, then this would make sense. I also observe several birds sitting in pairs, just touching bills quietly.
I have seen lots of Ravens heading in the direction of the Sedona roost as far away as Cottonwood - could the Cottonwood birds (20 miles away) be using the Sedona roost, at least occasionally? I also observe birds in the late evening that are nowhere near the roost - could they just stay out at night? Nesting Ravens are reported in several location in the area now.
April 19, 2001 - I watched the "Buttes" staging area from my vantage point a quarter-mile away. This evening they are in rare form. The winds are perfect for causing the rapid updraft that they love to play in. There are perhaps 250-300 birds in the air above the buttes as I arrive! This is the most I have ever seen there at one time. The weather is beautiful, warm and overcast. The acrobatics today are spectacular - everyone seems to be putting extra effort into outperforming the others. I see every acrobatic maneuver, including "hammerhead stalls", immelmann maneuvers, loops, rolls, "wifferdills" and a kind of flat spin wherein the bird turns slowly about its vertical axis as it descends. They also enjoy zooming up to a few hundred meters in the updraft, then descending slowly, "gear down" in a straight vertical descent. As an ex air force pilot I recognize the reasons and forces they must be feeling in these maneuvers and I can empathize with the joy and thrill they are experiencing (but it would be obvious to any observer). One game I see is a bird flying up into "parabolic" flight (the same maneuver that a pilot uses to experience sustained zero-G flight) and releasing a small rock or stick at the top, then following it down to catch it on the descent - what fun!
I see more stick games than usual, too. Lots of "trapeze" and feet-to-mouth exchanges, and "keep away", where the stick bearer entices others to try to steal his stick - the thief rarely succeeds.
Also tonight I saw lots of grounded behavior - agonisms between two males(?) - horns raised, neck puffed out, tail and wings slighhtly extended - try to look as big and menacing as possible. Then one will slowly sidle up laterally to the other and one or the other gives up and leaves - this seems almost more like a game than agression. I also observe reciprocal allopreening - one bird preening the head and neck feathers of the other, then they trade positions and the recipient preens the other - only on the head and neck. I wonder briefly why only the head and neck are groomed, then realize that the preened bird can't reach these spots with its bill, so other have to do it for him.
May 6, 2001 - This afternoon I gave them a real treat (I thought!) - I had found a freshly-killed Western Diamondback Rattlesnake on the road and I placed it at the normal "feeding" site. I stretched it out to look as natural as possibe (though it was in pretty bad shape and obviously dead). The first Raven to come by flew to within a few meters of the snake, then walked casually over to it, showing no particular signs of caution or fear. He inspected it from every angle as he walked all the way around it, never getting closer than a half meter from it. After a few minutes he left as unconcerned as he had come. The next Raven to visit approached cautiously, but no more cautiously that I see them do for a rabbit or other non-threatening food. He also inspected it from a half-meter or so, then left. No other birds visited the snake this evening, in fact very few (6-8) even came to the buttes before going to the roost. Most birds tonight flew directly to the roost and settled in. There are less than 100 birds roosting tonight - perhaps most of them are breeding and brooding in the area, and don't use the roost during these times? The weather was very warm and the birds that do show up at the roost show up at the last moment - when the sun is nearly down. As I sat at the overlook a Crissal Thrasher came by and serenaded me from a nearby treetop - quite a treat. I also was privileged to watch a pair of White-throated Swifts mate in mid-air twice.
Here are some examples of the sounds in both .WAV and .MP3 formats - these are well worth listening to - you will hear sounds you have never heard from this species before!
Sample 1 (60K, 2.8 sec.)
Sample 2 (180K, 8.4 sec.)
Sample 4 (193K, 28.2 sec., MP3)
Sample 5 (417K, 1 min, 25 sec., MP3) Listen to this one if you only listen to one of these!
Sample 6 (143K, 19.5 sec., MP3) Here are some "whines" and "mews" that are pretty interesting. These are the calls that I think may be imitations of juvenile begging calls (?).
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