The Daily Bucket is the place where we share the things we've seen in the natural world around us. It helps us keep track of the changes that occur as the seasons progress, whether those changes involve the weather, the plants growing in our yard ,the insects that visit them, or any of the other animals that we are fortunate enough to observe.
This past week the three of us took a couple days and went camping at a COE lake about a hundred miles to the north of here. The weather couldn't have been any better for camping and we would have loved to stay a few more days but were unable to do so due to prior commitments.
On previous trips we had seen Cliff Swallows that were colonizing the many bridges that cross the various lake arms, and we were interested in getting a better look at them since we never see them in our neighborhood, even though we are only a hundred miles south of there. We knew nothing about them other than the fact that they lived in large colonies and built very cool mud nests that were shaped more or less like gourds which they attached to the bridges. From their name it's clear that at one time they were cliff dwelling birds but a quick internet search tells me that they now nest on bridges and other man-made structures almost exclusively. The choice of bridges makes very good sense to me. There is no shortage of them for one thing. Plus they are almost totally immune to predator attacks other than aerial attacks from birds of prey, but I suspect that being excellent fliers, they aren't an easy prey and probably aren't targeted often. Most bridges also have sections that have the added advantage of some sort of overhang which offers some protection from the weather. Plus their main food item, insects, are usually plentiful around and over water. And of course on most modern concrete bridges there are plenty of flat surfaces with just the right texture for attaching their unique mud nests to. And obviously, there's always a good supply of mud all along the waters edge to use as nest building material. So it's no surprise that they've forsaken the cliffs and moved to the bridges.
We checked out three different bridges while we were there and all had fairly large colonies of swallows living under them so the population seems healthy, at least in that area. We used my old jon boat for our photography platform and it would have been perfect except for the fact that the wind blowing across the lake caused enough choppiness that the flat bottomed boat was constantly rocking. It wasn't a violent rocking but enough to make focusing difficult. That and the bright sun with resulting glare off the water didn't make for any award winning photos but we salvaged a few that show the birds well enough to introduce them to any of you that might have never seen them.
There were probably three or four hundred nests on each of the three bridges that we checked although I don't believe that all of them were active. Some appeared to be in decay while others seemed to be only partially finished. Many or them had adult birds inside but it was impossible to say whether the nests were otherwise empty, held eggs, or youngsters. In a few of them we could see birds that appeared to be very near fledging. The immature birds were distinguishable from the adults by their pale breast. All of the adult birds looked alike to me and I could see no differences between males or females. The flock sizes looked like they ranged from about thirty or forty to maybe seventy or eighty. Of course we had no way to know if the birds we saw were the whole flock or if others were out hunting somewhere out of sight. They were constantly coming and going, and it was impossible to keep track of individual birds for more than a moment.
It's difficult to see in this pic but that dark line just below the railing is a row of nests that almost completely fill this section of the bridge. Most sections aren't quite this full, and have groups of three or four nests, then a short empty space followed by three or four more nests, etc. etc. If you look close you can see a few nests on the pillars too. All the pillars had a few nests but none that we saw had very many. Curiously almost all nests were oriented parallel with the bridge,that is, they were placed facing outwards, on either side of the bridge, with none, or almost none, placed on surfaces running at right angles to the group. There were many other seemingly perfect locations that held no nests at all.
One thing very noticeable was that the birds seemed to arrive in groups and that the groups would concentrate on the nests in specific sections of the bridge, usually an area about thirty to fifty feet long. A large group of birds would be all over that section for a few minutes and then there would be almost no activity there for awhile and the birds would all be flocking around another sections. We wondered whether the birds were performing cooperative feeding where all members of the flock fed any and all youngsters or whether there were many different flocks that came and went only to their respective parts of the colony. I actually came away with more questions than I arrived with. As I mentioned above it was impossible to keep track of individual birds or even a whole flock as they were constantly flying around in every direction. To get a better understanding of the flock dynamics I would have to go there by myself and spend a lot more time studying them. Sitting in one spot, for long periods of time, is simply not something that can be done with an energetic five year old on board. ( :
Below on the right is one of the few youngsters we actually saw in the nests. There may or may not have been many more in the other nests but it was impossible to see inside to know for sure. But the adults were making many trips to and from the nests so it's almost certain that they were feeding nestlings. One thing that was a bit surprising to me was that we saw no gaping beaks sticking out begging for food like you see with most bird species. So maybe most of the young were too small to get to the entrance, or they just had better manners, or they simply weren't there. Impossible to know for sure. Sometimes the parents would cling to the outside of the nest with their head in the opening and other times they would enter the nest. Try as we might we couldn't see what the parents were bringing to the nests.
It was interesting to see that many of the nests had been built with mud of different colors. I suspect that's a result of rising and falling water levels in the lake which would expose different layers and thus different types of soil during the nest building process. They simply used what was available when they needed it.
I still don't know a lot about these remarkable architects. Do the colonies consist of many smaller flocks that operate out of specific sections of the bridge or is it all one big happy family. Do the birds act as a co-op, working together to build the nests and feed the young or does each individual pair take care of it's own? Why were the flocks working only on short individual sections of the bridge at any one time? What were the parents bringing to the nest, food or mud, and if food, were they feeding babies or their respective spouses. Someday I'd like to get back up there about this same time of year and spend a few hours observing them, hopefully on a less windy day so the boat won't be in constant motion.
Ok, that's it for me, your turn, what've you been seeing.