Archive for August, 2013

IN THE CROWS PATH

IN THE PATH OF CROWS

I’ve always had a casual interest in crows. Primarily for their social structure and intelligence. But I, like most people, have taken them for granted over the years. This all changed soon after our arrival in Southern California.

We were introduced to the Murrieta Crows Roost early after our California arrival in late 2009. While we were looking for a home we rented an apartment in Murrieta, CA. The apartment complex is located adjacent to the Murrieta Retention Basin. The retention basin contains water year round and is host to the largest contiguous forest of large trees in the area. The trees extend into the apartment complex area and our unit was located under a number of large trees. The retention basin is a terrific birding spot with a trail around its perimeter but the area doesn’t attract a lot of birders since there is a lack of parking in the area.

Murrieta Retention Basin-01-w

It’s easy to see that the large tall trees (pines, sycamores, eucalyptus, and others) provide the perfect place for a communal crows roost.

It rained for three straight days when we moved into the apartment and nothing out of the ordinary occurred, although the local residents thought three straight days of rain was quite “unusual.” At sunset on the fourth day we heard a lot of crows calling. We went out on the patio to see what all the commotion was about. It was quite a surprise as “calling” crows dropped into the trees by the hundreds. The crows would sit for a while then rise up and put down again. This went on for some time before they all settled down in the trees for the night. At sunrise the next morning all the crows were gone.

I asked some of the other residents of the apartments whether this was a regular occurrence and they casually responded, “Yeah, it happens every night!” From then on we witnessed the evening event on a regular basis making sure to get under cover on their arrival. It was common for the crows to “dump their excess baggage” before settling down.

A month and a half later we found a home five miles north of the Murrieta Retention Basin. We moved into our new home under a steady two days of rain. Our new welcoming neighbors remarked about the “unusual” amount of rain. During a downpour our first yard bird at our new home ran around on our front lawn occasionally posing on a boulders. The Greater Roadrunner welcomed our arrival. I took this event as a harbinger of more good birding things to come.

RoadRunner-20100206-02-w

After settling in to our new home, I had more time to start renewing my acquaintance with the western birds and to begin creating my new yard list. I also had time to enjoy the cool evenings in the backyard and immediately became reacquainted with the crows once again. Our new home is located “in the path of crows” that fly to the communal roost each evening from the north to the roost five miles south.

MAP-CROW FLIGHT area -N-w

Since first witnessing the crows roost and now living along the northern route of the crows, I have become interested in learning more about the nature and structure of the roosting crows. Apparently there is little known with regards to why, when, and where crows decide to share a common roost.

The website crows.net lists the number of crows at the Murrieta Crow Roost to be in excess of 3,000 birds. The site also indicates that there are only two crow roosts in Southern California.

I have been at different locations in the Temecula/Lake Elsinore valley in the evening and have observed crows flying to the roost from all different directions. It appears that the northern component (the ones that fly over us) make up at least one third to perhaps one half of the total roost population. This would make sense since Lake Elsinore and the area north of the roost site is more rural than south and east of the roost site. The area west of the roost site is the Santa small numbers of crows heading east to the roost at sunset.

crows at sunset-01-wcrows at sunset-02-w

I have conducted a number of crow flight counts to get an idea and to see if there are any patterns that might be of interest occurring. During the 2012 Christmas Bird Count, I counted 1,268 American Crows (AMCR) heading to the roost. During a BIG SIT in 2011, I counted 1,195 AMCR heading to the roost. I also conducted a 12 day count in 2011 which resulted in a 12 day average of 664 AMCR (9 days of 500 or more, and 2 days of inclement weather). Just this past week I was up early to photograph the full moon setting before sunrise – during that time I count in excess of 700 AMCR heading north from the roost site.

crows passing moon-01-w

It appears that there are three or four distinct flocks coming through each evening from the north. The first flock passes through just before sunset, the second flock shortly after sunset, and the third and fourth flocks closer to dark. There are always a few stragglers bringing up the rear. I’m guessing that the distinct flocks may be related to the distance the crows are from the roost when they initiate their flight (the first flock – closest to the roost, the remaining flocks- further away).

The crows roost essentially ceases to be during the breeding season with the exception a few non-breeding birds that continue to fly to the roost each evening. Soon after the breeding season ends and the young have fledged the numbers heading to the nightly roost start picking up again. During this time there is a lot of “calling” among the crows during the flight to the roost, perhaps the parents trying to keep the youngsters on task.

There appears to be a pre-flocking process that is used from time to time. Prior to initiating their flight to the roost the crows first gather at a staging area. A lot of “calling” takes place during this process and at some point a command is given and the flock of crows begin heading towards the roost site in silence. The staging areas appear to be random and may not be used on a daily basis. The purpose for these staging areas remains unexplained but may be weather related or perhaps staggering the flocks so they don’t all arrive at the roost at the same time.

crows-stormy weather-w

The line of flight of the crows each evening is weather dependent. Generally from our vantage point we can see most of the crows heading to roost each evening even if the flocks choose an alternate route. During inclement weather or heavy winds the flocks may be hard to see. The crows fly low in the valley and blend in with the trees along Murrieta Creek.

We are very fortunate that our new home in Wildomar, CA provides us the rare privilege of witnessing nature’s free outdoor entertainment almost every evening.

 

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Jim Lockyer
Wildomar, CA
BCDC WESTERN OUTPOST

"Travel is fatal to prejudice, bigotry, and narrow-mindedness, and many of our people need it sorely on these accounts.” Marl Twain