Interesting observations of Mtn. Chickadee and Western BB

The below is copied with the permission of the author. I hope you find these observations as fascinating as I did!
Julie

"On approximately 06/05/2009 we noticed a pair of Mountain Chickadees displaying feeding activity at a nest in a Ponderosa Pine at Spring Creek near La Grande, OR. Observations on three variably spaced subsequent days showed no change in the feeding behavior. In general, the chickadees would either fly directly to the nest hole or make a brief stop at an overhead dead limb before entering the nest hole with food.



On 06/16/2009, a stop by the nest revealed two frantic adult chickadees being held at bay by a very vocal female Western Bluebird that was alternating between being in the nest or immediately outside on a limb, frequently making threatening thrusts at the chickadees. During, approximately 4 hours of observation, the female bluebird left and brought food to the nest twice and nesting material three times. Meanwhile, the frantic chickadees would, on occasion, be successful entering the nest to feed before the bluebird would run them off. At least, three times the bluebird would return and enter the nest when a chickadee was still in the nest which would result in prompt expulsion of the chickadee. As the observation period went on, the female bluebird became more aggressive about chasing the chickadees. The male bluebird would show up intermittently but made no advances at the chickadees nor did he try to enter the nest.



On 06/17/2009, we watched the goings on at the nest for another three hours. Initially, it looked like more of the same, as the vocal female bluebird was throwing a fit every time one or both of the chickadees would show up to attempt to enter the nest with food. But shortly after we arrived, it became obvious that things were changing as the female bluebird showed less aggressive behavior towards the chickadees and they were repeatedly successful in entering the nest with food and sometimes then packing out fecal material. Over the observation period, the female bluebird made multiple forays to hunt, returning to the nest with food and on two occasions she removed fecal material. On two occasions the male bluebird brought food to the nest and passed it off to the female at the entrance to the nest. On one occasion the male bluebird brought in food to the nest when the female was not inside, entered and then came out without the food. On, at least, three occasions one of the chickadees was in the nest when the female bluebird entered and the chickadee was promptly ejected. On the day prior, we worried that the female bluebird might either kill the babies or cause them to starve to death. Now there was the question that they might be being overfed.



On 06/18/2009 we were only able to observe the nest for 45 minutes from 4:30 to 5:15 PM which was within the time period of previous days’ observations. The behavior of the chickadees had changed dramatically, in that, their approach to the nest was direct like it had been when viewed prior to 06/16/2009. The lone exception was when a juvenile sparrow was perched on a limb 8-10 feet above the nest. The chickadee bringing food then was all over the place flitting from one limb to the next, just as when the bluebirds had been present. It only entered the nest after the sparrow flew off. Strangely enough, there was no sign of the bluebirds during the entire 45 minutes.



On 06/20/2009, I watched the nest for 30 minutes. The chickadees made multiple approaches with food, often direct or sometimes with one limb stop before entering the nest as had been the pre bluebird pattern. Again, there was no sign of the bluebirds.



My take on this is that the bluebirds probably had a failed first nesting and so they were looking for a new nest site. Hostile takeover of the Mountain Chickadee nest looked to be the plan on 06/16. On 06/17 it appeared that adoption of the Mountain Chickadee babies might have become the motive. Then, perhaps, the male bluebird found an unoccupied, alternative nest site so the bluebirds gave up on their designs for the chickadee nest. Any thoughts?"



Ted-------------Just north of La Grande