Thursday, June 26, 2014

Barn Swallows Matter


As part of an on-line course called Animal Behaviour from the The University of Melbourne (via Coursera), there is a requirement to conduct an animal field study. I chose the Barn Swallow, a wonderful bird that heralds the arrival of spring and the beginning of fall. Their air acrobatics are a marvel to watch and their chitter every day when I tend the horses is comforting. Something I miss when they leave.Wildlife  are a measure of the environment. When they are abundant and healthy, at least the immediate environment is the same. This is why it bothers me that the numbers of swallows that have returned in the past few years seems to be on a decline. The bottom line-they matter!

I have been around these swallows for quite some time. They have always had a place in my barn and when they return in the spring, they usher in the end of winter. Depending on the weather, they arrive at my barn at the end of April or early May. The nests have been in my barn since we’ve owned it so the swallows do very little nest building, some repair, but basically they move right in to the available 20 + nests.
The number of returning, at least I think they return, varies each season. Keeping in mind our barn is for horses, five stalls, and not too large, we have had six to twelve mating pairs each season. A count can be difficult as they move around so fast it’s difficult to determine an accurate number. This year, 2014, there are 5 females and 3 males that I can verify. They are nesting in a few places not easily observable so there may be more.
What do they eat? From observation, their favorite food is other flying insects, predominantly: mosquitoes (yay), some black flies, knats, and other unnamed bugs. I have almost never seen them forage on the ground. They are said to eat seeds, but I have not observed that. While they do hunt solo, it is more often the case that they soar as a group, flying like fighter jets on the attack. They will dive close to the ground in formation, pulling up at insane angles, and grapping food on the way, only to swoop down again. The tendency is to skim about 2/3 feet above the ground for maybe 20-40 feet and then shoot back up higher, as if to get a better view of food sources. On hot, humid and even rainy days, most hunting is done this way. On clear, cooler days, time is spent at higher ranges, maybe 30-50 feet up, perhaps in search of insects other than mosquitoes that do not generally spend time at those heights. Feeding is generally done early mornings and evenings, times when most other insects are out and about. For the most part, the swallows stay in the immediate 4-5 acres of the barn for food, although it is said they will range for several miles-but we have enough bugs for them to neat and plenty of open fields. They are not hunters in the woods as, I suppose, their flying ability would be for naught among the trees.
Clearly, there is very little danger in the barn and aggressive behavior is minimal. Swallows often rest on stall doors, overhead wires, and low walls to watch the activity. On a rare occasion males may flutter at each other, females also, but there is no outward signs of attack. Efforts appear to be geared to drawing attention away from nests, but little direct assault.
Aggressive and non-aggressive interactions with other animals of its own or another species: “The barn swallow's close association with humans in Europe goes back more than two thousand years. It has been speculated that one reason swallows choose to nest on door stoops, light fixtures, and porch fronts is because the closeness to humans keeps away crows and other predators. The birds will even risk cat predation and human vandalism, and place nests close to the ground if the location is frequented by humans.” Most of the nests in my barn are about 8 feet from the floor, many even in the horse stall and alley way that is the place of much activity. When I do chores morning and evening, I’m accompanied by two dogs, a terrier and a border collie (who thinks the horses always need to be someplace other than where they are). The collie, in the a.m., enters with a non-stop bark, jumping on the doors of each stall. The swallows just watch this morning ritual with no sense of agitation. Several nests are located where I store some hay and when I enter that location, we are within 4 feet of each other and many times the swallows just watch me. On occasion, a male may flutter around me, as if to draw my attention from a nest just a few feet above my head. As the season progresses, they become even more comfortable with my presence and will let me within 2-3 feet, as opposed to the early season 4-6 feet proximity.
Other birds around the farm, of which there are many, pretty much leave them alone and vice versa-none can match their flying skill so peace prevails among the species.
Mating and courtship behavior:These birds are generally monogamous, males mating with a single female. Although rare, males sometimes will pair with 2 females. My guess is that given that I have more females than males, that the males are servicing more than one female.
Paired swallows will aggressively defend the small area around the nest and guard his mate from other males that might attempt to copulate with her.” ( I have not, in all the years of my exposure to swallows, seen a mating ritual. My suspicion is that swallows pair-up in what would be my winter, but their summer. Keep in mind that swallows, “…migrate south to tropical Central and South America. . These swallows, called "neotropical migrants," spend 6+ months in southern locations before returning north in spring ….” It is said that they may mate here, but when I see them in my barn, mid-April or early May, they are already paired and settling into the nests they have chosen for the year. “The male barn swallow returns to the breeding grounds before the females and selects a nest site, which is then advertised to females with a circling flight and song.” It always seemed to me that both sexes arrived at the same time. But I will have to admit to seeing males circling nests and chittering, clucking, and basically ‘talking up a storm,’ so this may have been the ritual that has been mentioned, but it also seemed to be very brief in duration. Also, I have noticed that when I do get close to a nest, the males start squawking and flutter about.
Breeding patterns: Nests contain between 3-5 chicks. Generally, survival is quite high. There have been a few instances when a baby feel from the nest; on one occasion I was able to return a chick safely to the nest. Every now and then I have found a dead chick in the nest, usually in extremely hot weather. Incubation is about two weeks, at the low end when hot, a little longer if cool spring. Both parents bring food to the hatchlings. Once they learn to fly (about 3 weeks), the babies roost in, on, or beside the nest for at least another week. Past experience indicates that the babies and parents hang around the barn and area for the duration of the summer.
Differences in coloration between individuals and/or the sexes: (Hirundo rustica) Swallows have a long, slender, forked tail. It has blue-black upper parts, a reddish throat and breast, and a rust or buff colored belly. Females are lighter  in the belly and shorter-tailed than males.
Energy Budget: From my observations, time spent on tasks appear to change based on the basic needs at hand. When the swallows first arrived most of their time, 60-80% was devoted to getting food. Perhaps this was the result of needing to re-fuel from their migration? The rest of the time seemed to be devoted to picking nests and resting. That accomplished, more time, 40%, is spent in the nests, 20% hanging around and 40% on food. Food is plentiful so it’s not essential to spend lots of energy trying to find some. I’m sure this will change when chicks hatch. As of June 25th increased time is spent nesting and I thought I heard some peeps from a secluded section of the barn. Babies? False alarm, no babies yet. But will post pics when hatched. (NOTE: Sorry about the low quality of the pics in the barn. It's dark up in the rafters and they just do not come out well.)

Anecdotal note: Several years back there was a banner summer for swallows. At one point I counted sixty. At the end of the summer, they all just seemed to disappear. Then one September morning after feeding the horses, I saw that the 60+ swallows had returned and were sitting on the power line between the house and the barn. Then, in unison, they all rose like a wave in the ocean, did a big arcing circle around the barn, and then they headed south. I like to think that they came back for that last visit to say goodbye. Who knows?

Cause for Concern: I must add that things are not quite normal this year. As of July 1st, there have been several hatchlings, but I have also spotted some broken egg shells under several of the nests. There are no predators in the barn. Also, the normal baby chatter is not present. In years past, when the eggs hatched, every morning and evening during chores, the babies would respond to my voice and cry for food, their little orange mouths wide open, forcing parents to respond. This year, this has not happened. Suddenly there were a few babies hanging out without all of the fanfare. Overall, the adults are more quiet than normal and the pace seems subdued. yes, we have had some very hot weather these past few days, but this has not normally been an issue. It was also not uncommon to see the adults on the power line from the house to the barn. So far, this has not really happened. Just all seems a bit off! 

July 10th update. There are 3 new babies! However, while there are several females around, most of the males have gone somewhere else-perhaps they're off with other females? It appears that the first hatch birds have not stayed around. Plus, I only see a couple of swallows hanging out on the power line between house and barn-more accustomed to seeing scores by this time of year. Females appear to be doing a good job feeding the babies. 

July 14th. Lots of new activity. More females around but few males. One female did a happy dance for a female and then flew out of the barn, the female hot in his tail. Suspect there may be more mating in the wind. Babies are out of their nest but still staying close. So, not sure where they all went for a few weeks, but this morning the barn was filled with swallow chatter. 

July 21. There are now 16 sparrows that are hanging around and can be seen on the  power lines mornings and evenings. It's a bit more normal. Can't help but wonder if there's a shift in their season due to climate changes here or south of the border and that behavior I observed in the past is sliding later into summer. Nonetheless, good to see them each morning and that so far the hatchlings appear to be thriving.

 Man, that Border Collie is noisy!