SWALLOWS (Hirundo rustica)
By Nasif Nahle


Five years ago, some new boarders arrived to our laboratory. At the launch, some of ours employees worried about it because they had heard many legends about swallows (Hirundo rustica), for example, that swallows’ excrement could cause blindness; that the swallows were the souls of the deceased, etc. Even, a person said that the swallows conveyed good luck to their hosts, in this case, to Biology Cabinet. Obviously, these are just fables.

But it is true that swallows (Hirundo rustica) are carriers of mites (acaridae like Carpoglyphus nidicolous that inhabits in swallows' nests and other species that damage the feathers and skin of swallows from the superclasses Pterolichoidea and Analgoidea) and dangerous bacterial and viral diseases. The last can make ill to mammals and usually they are transmitted by mosquitoes. The main diseases carried by swallows (and other migratory birds) are the West Nile Fever, Equine Encephalitis (Encephalitis of horses and other mammals like humans, cattle, etc.), and many bacterial diseases, as pseudomoniasis (caused by Pseudomonas aeruginosa) and salmonellosis (caused by Salmonella typhi), and fungal diseases. Among the fungal diseases carried by swallows, the most dangerous for human life is hystoplasmosis, a lung disease provoked by the microscopic fungus Hystoplasma capsulatum. Hystoplasma capsulatum grows into the intestines and lungs of birds, bats and other feral mammals, all of which expel the spores of Hystoplasma in their excrements.

If you love swallows and do not wish to get rid of them, then you have to be extremely careful when cleaning the excrements of these birds. It would be better if you use a protective mask for eyes, nostrils and mouth, latex gloves and latex boots when cleaning the place where swallows have their nests. I have another advice for you, when cleaning the place where swallows dwell in, use abundant water to drag the debris thrown by the birds. After cleaning the place, you should wash your hands with water and antibacterial soap.

Well... our swallows (Hirundo rustica) decided to dwell at one of the corners high under the roof into the laboratory laundry. We built the laundry on the eastern part out from the main building (on the yard). It is a humid, warm and attractive place (at least, attractive for swallows).

The first indicator that we saw about the presence of swallows were some small patches of mud with bits of dry grass and other herbs, and small branches of mesquite adhered to them, distributed on the upper third of the walls of the laundry. Approximately, after eight days, we saw the completed swallows’ nest in the upper corner under the inner roof of the laundry. Right away, I considered the option of observing them during the time that the swallows remained in our laundry. Well, five years have past since the arrival of the swallows and I have had time enough to observe them unhurriedly.



I noted a sexual dimorphism in the observed couple of swallows (Hirundo rustica). Although it has been written that these birds do not present such dimorphism, the male has a more rounded and larger head than the female, as well as the yellow ochre of male's chest, which is darker (almost raw sienna) than the female’s chest. The caudal feathers of the male are longer and more opened than the female's caudal feathers (in any case, in the first observed couple). The second year I saw the same couple arriving to the nest, but the third, fourth and fifth years the female came here with a different groom each time.


The male begun the construction of the nest. At first, the groom was placing on the walls small patches of mud with small fragments of plant branches stuck on them. The male distributed those small patches of mud on diverse spots of the walls that he had selected previously. While the groom was doing this, the female was flying expectantly from one place to another. When the groom found the most suitable place, it began the definitive construction of the nest. It was that moment when I verified that the girlfriend sporadically was aiding for the construction of the nest. This behavior is a reproductive improvement because the labor division accelerates the building of the nest and thus increases the possibilities of breeding more than one set of offspring per year. The swallow male finished the nest with the sporadic aid of the female. Sometimes another male came to help, but the bride did not seem to be pleased.

Once the nest was finished (March 13, 2000), the male perched on an ornament on the wall of the terrace at a high place, nearby to the nest, and emitted twice or three times a long and very adorned sequence of chirps and a final prolonged squeak (somewhat similar to too-tee, too-tee, too-too-tee, too sheeeeeeerp). In a few seconds, the bride, which laid down on a wire at some 23 feet (around seven meters) from the groom’s place of rest, flied to the area where the groom was resting, the male emitted two short shrieks and the bride flied to the nest, where she positioned herself to expect the arrival of the male. The groom emitted two short shrieks and followed the bride to the nest. There, both exchanged a series of quick and short chirps. Then, they copulated. They can repeat this throughout daytime and in the course of two or three days.


One day after the coupling, the swallow laid three eggs (it was the first time that I observed it, because that year, on a second cycle, I observed that the female laid five eggs!). The eggs were around 14.8 mm long and the eggshells were yellowish with many small brownish or grayish stains on them. Many of those tiny stains were almost triangular, although most of them were asymmetrical.



Both, female and male contributed on the incubation of eggs. I observed that from time to time, the female abandoned the nest for long periods, while the male occupied the mother's place on the nest. The incubation lasted eight days. I have read from other authors that the time of incubation for swallows varies from 13 to 16 days; however, I think that the shorter time observed on my swallows obeyed to the heat radiated down from the roof. I measured the temperature at that corner and the thermometer rose 118° F (48° C). THROUGH THE FIVE YEARS OF OBSERVATION OF Hirundo rustica, I DID NEVER OBSERVED THE MALE  FEEDING THE FEMALE. What I observed was that the female abandoned the nest for a period of three to five hours during the warmest hours of daytime, perhaps to feed itself.

For example, on July 9, 2005, I observed along the day the behavior of the female swallow. The hours here noted correspond to the normal time, not to the save daylight time. I have emphasized on red the texts in line with the longest time of abandonment of the nest:

05:35 hrs = the female abandoned the nest and flew toward northeast. Environment T = 76.64° F (24.8° C).

07:50 hrs = the female returned to the nest and remained hatching the eggs. She remained there until 12:45 hrs. Environment T = 81.14°F (27.3° C). 

12:45 hrs = the female abandoned the nest and flew toward northeast. Atmosphere T = 93.38° F (34.1° C).

16:20 hrs = the female returned to home, but she never settled on the nest, but on the lamp at the backyard of the laboratory, on the point of the laundry. Atmosphere T = 101.66° F (38.7° C).

18:04 hrs = the female flew again and was directed toward the northeast. Atmosphere T = 99.14° F (37.3° C). She did not settle on the nest from 16:20 to 18:04 hrs.

18:15 hrs = the female came back to the nest, but she remained resting on the lamp at the backyard of the laboratory. Environment T = 97.70° F (36.5° C).

18:35 hrs = the female flew towards East. Environment T = 95.54° F (35.3° C).

18:51 hrs = the female came back and rested on the nest. Environment T = 90.32° F (32.4° C).

It has been almost the same behavior since the swallows have been visiting us; however, the total time of neglecting the nest was restricted to some 30 minutes until some two hours. When the male was absent, the nest was deserted by further and longer times.

I have observed also that the female was out from the nest along the warmest hours of the day. When I measured the temperature of the nest, I found it was at 118.4°F (48°C) at 15:30 hrs! I was concerned about the survival options for those eggs this summer. Maybe, we would have fried swallow’s eggs that weekend.

When the male was at home, the couple took shifts to take care of the nest; but, now that the female is alone, the nest remains without protection during more than one half of a day. By the way, the second male abandoned also to our beautiful bride. Perhaps she was on a bad mood?


After eight days of incubation, three young birds hatched; two females and one male. Unfortunately, only one female survived because when the parents came with food, the lost female remained behind, while the other little birds appeared their heads over the edge of the nest to be fed as soon as their parents arrived with food. Thus, the young female, which all the time remained behind her brothers, died by lacking of food, while her brothers grew spirited, strong and lovely.

The young birds of Hirundo rustica also show a sexual dimorphism: Male chicks have two delicate feathers, one on each side of their heads, while the female chicks do not possess those feathers. When they grow to adults, the males lose those juvenile feathers.



14 days after hatching, the two young birds were encouraged by their parents to leave the nest behind. It is time for a new brood to take up temporarily the nest. Each time and one at a time, the young birds were incited to fly. First, the mother emited a chain of dual chirps, one long chirp followed by a shorter one (too-tee) until one of the young birds is encouraged and flies out from the nest.

I noticed that the first on leaving home was a female young bird. At first, she made a short jump of about three meters. Then, she rested on a peg for one hour and four minutes. In the meanwhile, the mother pushed the male young bird; then, she flied to one side of her chick through about six meters. The young male stopped on the lintel at the back entrance of our laboratory. He remained there for about three hours. From time to time, the mother pushed her sons to mend the flight by means of quick -apparently special- chirps. The female young bird mended the flight over 20 or 30 meters, but she had to stop on a street electricity wire. She remained there by a few seconds, until her father arrived.

The father made his young daughter to follow him by flying toward the northeast by means of a series of brief and strident chirps. The young male remained on the lintel of the back door. In the meantime, both father and mother kept on bringing food to their descendant. I could see that they brought dragonflies, worms, seeds, caterpillars, etc. for feeding to their young son.



After 40 minutes, the young female returned with her father. She was resting on a clip into the laundry for 3 hours and 24 minutes. In the meantime, the young male flew from the back door lintel, over near two meters, to set down on a streetlight of the laboratory. The parents kept on feeding to the young birds all along the time when they were resting; the female young bird was resting into the laundry and the male young bird was resting on the streetlight of the laboratory.

Then, it was the shift to the male young bird, which was urged to fly next to his two parents (I had the feeling that the male young bird was not as brave as his sister was). I decided to follow them on my car… It would be a major mistake if the birds had not rested, from time to time, on the branches of the trees along the route (ha, ha, ha). The total time they spent on resting was about 15 min.

After all, my snooping yielded fruits, since in 25 minutes we were in a paradisiacal place (at least for swallows). It was a swamp surrounded by mesquites (Prosopis juliflora) and stumpy huisache trees (Acacia smallii), warm and… PLENTY OF FOOD! Hundreds of insects, especially dragonflies and butterflies, were flying above the surface of the pond. The grass and the bushes that were growing there had branches and pods that looked similar to those small branches and pods that the couple was bringing when building their home. There, in the swamp, I learned that the parents not only taught their offspring to fly, but also to feed and drink water themselves.

I came back to the laboratory fascinated by what I had seen barely two hours ago. I almost grew enough to be an Ornithologist! The marsh is at 10.56 mi (17 km.) from the Biology Cabinet Laboratory. If we take off the time that the swallows spent on resting on trees, the parents and their chicks would spend only 10 min to reach the swamp. I assumed, not inferred, that the swallow parents had made the same with their daughter when they were absent from the nest by about 40 min.

What is the evolutionary benefit of taking the chicks out to a place so far from the nest? Apparently, the cost-benefit of this training would be disadvantageous by the expenses of energy and time. Nevertheless, I think that those chicks will foster new families by the next year; then, this strategy would favor the dispersion of the group toward new areas around the small lake. Besides, I think the habit of drinking water when flying, sweeping speedily the surface of water, and the detection of regions where they can obtain clay and small branches to build their nests are strategies learned from parents; thus, the statement of “taking the chicks to know the lake”, could be changed to “taking the chicks to know the high school”. Strategy implies any evolutionary empirical scheme associated with beneficial consequences.

Definitely, our swallows had a second strategy that depended on teaching the chicks to hunt in the area not far off from the nest; indeed, I observed that the parents showed their children to hunt dragonflies and butterflies while flying. Later, I could observe the chicks catching dragonflies when flying and "playing" into a periphery of some 200 meters from the nest.

Well... When I arrived to Biocab's laboratory, the male young bird and his two parents were resting -lying on a streetlamp- under the shade of the laundry build's brink.



None of us would be willing to leave our mother's home so easily. It is by the emotional burden that it implies. Through two and one half days (about 40 hours), the swallow parents impeded their brood to approach to the nest. Coldly, the swallow parents maintained their young birds laying down on the streetlamp under the eaves of the building. Occasionally, the parents took them away from home to fly during some hours and returned at the sundown for sleeping together under the eaves of the launderette, no more in the nest. The young birds have not returned to the nest since their parents carried them away, perhaps for the offspring started on their own life.



It has been written too much about the disloyalty of the swallow females; but it has never written that, perhaps, the male birds are who leave the home to target another females. The following years, after the first nesting, the female came back home accompanied each year by a different male swallow. Maybe, I will die and I will never know the truth behind this peculiar behavior. The husband is the last one on knowing about it!

It is the 8th day of July 2005, the fifth year of observations on Hirundo rustica. The bride has changed of groom for the first time on the same year... They have nursed four chicks. What happened to the first groom? I do not know, but I feel that that grisly male went into an "illicit" affair while her consort was engaged on incubating their four eggs... Perhaps, that poor guy has died. I do not know.

The female swallow is five years old. I think she will die soon because her natural life-span barely extends from four to seven years.



Swallows are self-sufficient and tend to avoid the close company of human beings, so you do not have to apply extra efforts to care of your boarders.

However, some individuals adapt to the presence of humans and accept some selected foods provided by humans, whenever this does not oust a human smell.

Swallows accept small balls designed for sweet-water aquarium fish and for birds. Get foods that have been made with insects like grasshoppers (for example, Schistocerca sp) or home flies (Musca domestica), fruits, sweet water crustaceans (Daphnia pulex, etc.), or a mix of insects and fruits. The producers of food for fish and birds specify the content on the canisters labels. Remember not to touch the food directly with your hands; use a new kitchen ladle exclusively to place the food in the feeders.

A good idea would be to set the bird feeders at a high place, not to far from their nests, where swallows can have a safe immediate and easy access. Many gardening retailers offer bird feeders with a siphon that generates a cascade-like water flow. You can place it at your backyard, which can be especially attractive for swallows.

Author: Nasif Nahle. Biologist


BEHAVIOR OF SWALLOWS (Hirundo rustica) [Copyright© 2005]
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Click on thumbnails to see enlarged images:
Hirundo rustica chicks.
Copyright© Nasif Nahle. 2005
Hirundo rustica male warming five eggs.
Copyright© Nasif Nahle. 2005
Hirundo rustica male calling the bride.
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Hirundo rustica male resting on a garnish.
Copyright© Nasif Nahle. 2005


Hirundo rustica male ill.
Copyright© Nasif Nahle. 2005