Thursday, April 13, 2006

Acorn Woodpeckers on My Morning Bird Walk

I've been giving my new birding binoculars a workout. I've been going on the field trips associated with my birding class every weekend. And I've returned to my morning walks for exercise. But now those walks are all about sighting and identifying birds. What fun! While I have to admit that constantly interrupting power-walking to see a bird isn't the best way to get a cardio-vascular workout, I am walking farther and climbing higher hills. I hope that makes up for the frequent stops.

I'm also taking my digital camera along on my morning walks. I've been wanting to photograph birds for sometime now. It's good to have a photo (even if it is poor) to help remember the bird I want to identify. My goal is to become a good photographer. As you can see from the photos I took today, I have a long way to go.The photos, by the way, are of Acorn Woodpeckers (Melanerpes formicivorus) in case you can't tell. I was so excited when I saw these birds for several reasons. First, they are striking to look at . . . sorry my photos don't show how beautiful they are. And yes, they do have red "caps" on their heads. And their behavior is just as appealing as their bright little black and white suits. As you can see the single bird in the photograph (above) was in the company of two others (left). Time slipped by quickly as I watched these gregarious, social birds.

We have oak trees in our neighborhood and it seems reasonable to assume that the "nut" I saw one of them trying to store in a hole was actually an acorn. It was interesting to watch the bird try to find the right hole in the palm tree to fit the acorn. That is another aspect of their behavior ... storing food. I've seen photos of oak trees absolutely studded with stored acorns. I never thought I'd witness this behavior myself.

I love learning facts about birds. To this end, I've decided when I have an especially good sighting or see a new bird that I'll spend some time to learn something about them. It is part of the fun of bird watching. So far, here is what I've learned about Acorn Woodpeckers:

The size of Acorn Woodpeckers is 9 inches overall with a wingspan of 17.5" and they weigh about 2.8 oz. They are very vocal and were constantly chattering and calling to each other while I watched them. The sound they make is quite distinct and pretty much unforgettable. It will most likely be one of the first bird sounds that I'll be able to identify when I go to my Birding By Ear class tomorrow morning.

Besides being cavity nesters, they store food. All the food storage that goes on is to build a cache of food to carry them through the winter. These woodpeckers have an investment to protect so are very territorial and vigoroulsy defend their "grainery". This defense is not only against other Acorn Woodpeckers, but also against squirrels and jays. To store the food an Acorn Woodpecker will excavate a hole in the tree or telephone pole to hold the acorn. It takes from 30 to 60 minutes of drilling time to make the hole. That's pretty awesome and almost unbelievable when up to 11,000 holes have been found in a tree. No wonder they have a strongly ingrained defense mechanism. They have a lot of time and energy invested storing the food they must have to survive. Acorn Woodpeckers will also defend trees that are riddled with empty holes.

Then there is polyandry. What is that? Well, it is where females pair with several males. The males then incubate the eggs and care for the young. The females defend territories, compete for mates and take the lead in courtship. There are two types of polyandry -- classic and cooperative. Classic is where the female divides her attention among two or more mates. Cooperative polyandry is where several males cooperate to assist a female. Acorn Woodpeckers fall into the 'cooperative' group.

One other aspect of Acorn Woodpeckers is also fascinating . . . they form family groups. There are several factors which lead to this type of cooperative social unit. First, there may be a shortage of quality territories which discourages dispersal of the young woodpeckers. Or there may be a food shortage during dry years which leads to recruitment to help feed the young. More recent theories suggest that along with habitat saturation there may be social benefits, such as improved survivorship and the learning of skills which creates an extended period of apprenticeship.

I've learned just enough about Acorn Woodpeckers to whet my appetite find out more. Guess I'll have to add a book to my "I-want" list that provides more information on Acorn Woodpeckers.

1 comment:

Jana said...

I have a colony of these birds that have lived in two locust trees right next to the house for the last 35 years.
They are facsinating to watch, I often sit on the deck with field glasses. I assist them in defending thier granary trees from the local crows. They also war with the neighborhood scrub jays - it gets noisy!