We have three species of swallow in the United States that have the potential to cause damage in a residential setting. The Cliff Swallow (Petrochelidon pyrrhonota), Barn Swallow (Hirundo rustica) and Violet-Green Swallow (Tachycineta thalassina).
The most common species that we see building a mud nest on the side of a house is the Cliff Swallow or Barn Swallow. Of the two, the Cliff Swallow is a colonizing species. While it may be a pleasant experience to have a nesting pair of Barn Swallows living at your house, it is an oppressive and sometimes threatening experience to have two hundred Cliff Swallows building mud nests under the eaves of your home. The mud slinging begins at sunup and reaches a fevered pitch by mid morning. Cliff Swallows then usually take a mid day rest period, gather their strength and then begin a full-scale evening assault. The end result of all this work is at the very least, a lot of mud on the side of a house. Left unchecked, Cliff Swallows will build hundreds of mud nests along the side of a home, in the shade of the eaves.
We have not experienced a problem with Violet-Green Swallows until this year. In that case, Violet-Greens’, who are primarily cavity nesters, had begun to nest on a bridge along with Cliff Swallows. We believe this was an isolated case of species adaptation to available nesting habitat.
Cliff Swallows need three things to nest successfully. First they need a water source. Their nests are built completely out of mud balls, which they gather from a pond, stream or riverbank and pack onto the side of a wood or masonry (stucco) building. Cliff Swallows’ nests are a complete gourd shaped nest with an opening just large enough for entry. They can fully complete a nest within two days. Most commonly, Cliff Swallows will take 3-4 days to build their nest, but as they do not need a nest to breed, they can work faster as the female feels pressured to lay eggs. Barn Swallows do not complete the gourd, leaving the top of the nest open. In addition, Barn Swallows use sticks and feathers during nest construction, while Cliff Swallows use mud only.
The second thing Cliff Swallows need is bugs! They primarily feed on flying insects, which are common in areas where there is water and vegetation. Finally, Cliff Swallows need shade. An enclosed nest, built in the sun will quickly cook the contents. This is why they build directly under the eaves of houses instead of anywhere on the side of the structure. This is an important distinction for a NWCO to make when deciding what to net on a structure. If the area receives sun for the majority of the day, Cliff Swallows will usually not build there. In addition, this requirement for shade gives us some insight as to why they find houses so attractive. How many cliffs do you see that have a standard 2-3-foot overhang built in to facilitate a shaded nesting area?
Cliff Swallows are one of our many federally protected bird species. In California, the Cliff Swallow nesting season is recognized as March 1st to September 1st annually. The significance of this is that it is permissible to destroy a completed nest outside of the recognized nesting season. After March 1st completed nest destruction is considered a method of “take” under the guidelines of the Federal Migratory Bird Treaty and is punishable by fines of up to $10,000.00 per occurrence by the U.S. Fish and Wildlife Service. The key word here is completed nests. Nests under construction may be destroyed as the criterion set forth for “take” in the Federal Migratory Bird Treaty defines egg protection as one of the objectives. An incomplete nest will not have eggs in it. It is not possible to tell whether or not a completed nest has eggs in it so therefore it must be assumed that it does.
A homeowner or NWCO can hose or knock down incomplete nests as a control method; however, this becomes a daily test of wills between man and bird. Once Cliff Swallows nest in an area, they become very site specific and surviving adults and first year birds will return to the same area year after year to nest. This battle of wills usually results in a severely mud stained house and finally, exclusion being the permanent solution to move the birds to find another site.
The full range of bird hazing techniques have been put into play in an attempt to passively discourage Cliff Swallows from building their mud nests under the eaves of homes. Tin pie pans, scare eye balloons, red and silver flash tape, plastic owls…. All have been tried and all have failed. Noisemaking devices have totally failed leaving the homeowner with one choice-physical exclusion.
We have had success with light duty black ¾-inch mesh extruded plastic netting attached to the facia and pulled at an angle to the side of the building. This material is inexpensive, easy to cut to fit, and because it is a semi-rigid plastic material, it doesn’t take a lot of effort to install it straight. The biggest concern for a homeowner is usually appearance. However, this lightweight plastic netting can be stapled to the facia, eliminating the need for a support cable. On wood structures it can be stapled to the side of the house as well making for a very fast and economical installation. On stucco houses, masonry anchors and a lower support cable can be used. We also will use adhesive backed hook and loop Velcro for net attachment, which will stick to stucco with a little additional adhesive, when we are making seasonal or temporary applications.
A well-done net application under the eaves is nearly invisible from 50-feet or so because it is in a shaded area and “gets lost in the shadows”. Every year we get the request for “clear” plastic netting for home installation. While this product works well, it is easy to see that a light colored net reflects more light and is therefore more visible than a dark colored net. If you have the choice, always use a black net for swallow exclusion, the finished product will look the best.
Most homeowners like the idea of putting the net up for the 8-10 week period required to keep birds off their house and then removing it for the balance of the year. Once netting has been installed for a season, and nesting successfully discouraged from the structure, bird pressure the following year is noticeably lower. This is not to say that houses in areas such as lakeside communities will not receive annual pressure. Some locations will always attract Cliff Swallows one year to the next.
The Cliff Swallow population is thriving. They have plenty of available habitat, ever expanding nesting opportunities, minimal threat from predators and an abundant food source. If you haven’t been contacted by a frustrated homeowner to solve the problems caused by a nesting colony of Cliff Swallows, expect it to happen soon. Equip yourself and know that you can solve their problem quickly and professionally without having to consider any lethal options. This is always attractive in today’s public eye and provides NWCO with another opportunity to be the good guy with the right solution.