Do not keep the bird’s nests. With the exception of the species listed below, you may be in violation of the Migratory Bird Treaty Act (full text with links) of 1918 - the following is from an inter-office memo:
The Migratory Bird Treaty Act protects all common wild birds found in the United States except the house (European) sparrow, starling, feral pigeon, and reisdent game birds such as pheasant, grouse, quail, and wild turkeys. Resident game bnirds arte managed seperately by each State. A reference list of migrqtory game birds is found in Title 500, Code of Federal Regulations. Part 10.
The Migratory Bird Treaty Act makes it unlawful for anyone to kill, capture, collect, posess, buy, sell, trade, ship import, or export any mirgatory bird, including feathers, parts, nests or eggs.
Historically, the plumage from many migratory birds was highly desired by the millinary industry to the extent that the populations of some species were rapidly diminishing. More recently, with the popularity of Natie American artifacts increasing, a lucrative market still exists for migratory bird feathers and eagle feathers to decorate many curios and art objects. Enforcement officers have no way to determine whethers feathers used in artwork were found on the ground in one’s own backyard, or if the feathers came from a bird that was killed illegally. These prohibitions are therefore intended to eliminate any commercial market for the birds themselves, as well as their feathers and parts.
There are a few exceptions to the prohibitions:
- Scientific Collecting Permit
- Falconry Permit
- Taxidermy Permit
- Native American permit to possess eagle, eagle parts and other migratory bird feathers for use in religious ceremonies (not for resale or transfer)
Violations of the Migratory Bird Treaty Act, Eagle Protection Act, and Endangered Species Act are considered criminal offenses and can result in significant fines and imprisonment. In some cases, a conviction might also result in the forfeiture of equipment (vehicles, boats, airplanes, weapons, etc.) used during the commision of the crime.
In a nutshell - leave the nests where they are. Apart from the possibility you may be breaking international law**, the nests may be reused by the same birds or another species, even in that same breeeding season (some birds can have two or more broods in a season, depending on many circumstances.
Make your own decorative bird’s nests using interlaced sticks and greenery (I’m sure Martha Stuart has a chapter on this somewhere). By making your own, you are less likely to bring in bird mites, lice and diseases (avian pox - not harmful to humans, but can be nasty to pets) into your house.
** The MBTA was signed by the U.S., Mexico, Canada, Great Britian, Russia and Japan. Other countries may have their own laws and statutes protecting local and migrating wildlife, but even if they don’t, how would you feel if you came home and found your house in a museum?