Barn Swallow

The Barn Swallow prefers to build its nest in stables, barns and other such structures, ideally with a beam ceiling. Alternatively, it can nest in any sheltered location (such as garages, cellars, sheds, verandas, etc.) provided there is permanent access. The nest is made by the female, using mud collected from the edge of water which she forms into pellets, giving the nest a unique granulated look. She adds twigs to maintain stability and cohesion. It is a permanent nest that can be reused for several years. It has a half-cup shape depending on where it is built; when against a beam it can reach up to 2cm wide and 1cm tall. There is no distinct entryway and the nest is always very close to the ceiling for added protection. The inside is lined with dry grass and feathers. An analysis of a nest revealed it was made up of 212g of dry earth and 2,224 rootlets and more than 1,100 trips were required to build it (La Hulotte n°60, pp 12-17). Interestingly, there have been reported cases of Barn Swallows collecting fur from cats to line the nest. When the weather is favorable, it takes about eight days for the nest to be completed. Adults prefer to reinforce existing nests than build a new one, leading to competition for the best nests at the start of the season.

It is not uncommon for other species such as the Common House Sparrow, Common Blackbird, Grey Wagtail or Wren to take over the nest.The Sparrow is the most annoying as it is able to expel its rightful owners. The first broods occur from late April to June. In our temperate regions, this may be followed by a second clutch, more rarely a third. Cases of four successive clutches are cited in the literature. The nesting period ranges from April to August. The female lays 2 to 7 eggs, usually 4 or 5, pinkish white and speckled with brown, which she will brood almost alone for 13 to 16 days. She leaves briefly to go and feed herself. Brooding also allows thermoregulation of the eggs when the nest is exposed to high temperatures, for example in an agricultural hangar in sheet metal. The young stay in the nest for about 3 weeks. Their weight will peak at 22 grams, 5 grams more than the parents, at 13 days. This excess weight will be quickly lost afterwards, especially due to the growth of the plumage and flight. Around the fifteenth day, when the feathers are developed enough to keep body heat, the parents no longer shelter them during the night, and only intermittently during the day. Then around the 20th day, the parents will stop feeding them in the nest. To force them to leave the nest and take flight, they approach them with insects but without giving them. Driven by hunger and forced by the cries of adults, the young will eventually throw themselves into the void, the flight being instinctive in them. Although the parents evacuate the fecal sacs of their young, the edge of the nest is filled with droppings as the breeding progresses and many of them fall to the ground below. It is this dirty side of the nest that puts off some people who for that reason don't accept Barn Swallow in their home. Quickly, the couple can start a second nest if conditions allow, the male taking charge of feeding the juveniles from the first clutch until their emancipation around the 35th day of life.All nesting is not successful. It is common for a clutch or a hatch to be lost. Infertile, infecund, or unfertilized eggs are common among passerines. A survey conducted in the 1970s and 1980s in Moselle (J. Meguin, private communication) can help us understand. In 1978, a fairly high mortality rate was noted at the egg stage. It affected 51 broods out of 608, or 8.5% of them, including 21 complete abandonments. In 1980, the proportion was 12%. As for the clutches, their survival depends on the weather conditions that influence the frequency and quality of feeding. In 1978, 32 clutches out of 608 totaling 87 nestlings were found dead. It was observed that when the search for food is made difficult, adults manage to feed the nestlings as best they can until their tenth day, but beyond that age, young ones eventually die of malnutrition, not having the necessary amount of food for their growth.