If you tried to get your trees trimmed in spring but couldn't because the tree service you hired found a bird's nest, you may try again during summer — only to find tree services still warning you about trimming trees now. This isn't because they don't want to help you. This is because two situations can occur in summer that make it inappropriate to trim now. But there is light at the end of that tunnel, and if the situation is urgent, the tree service will still help you.
Birds Will Nest More Than Once
Bird nests are protected by law; you can't cut trees that have birds actively building and living in nests in the tree. Even if the branch you need to trim isn't the one holding the nest, the work could disturb the birds. The federal Migratory Bird Treaty Act protects birds from anything that could be considered disturbing or harassing. What gets really frustrating for the tree owner is the fact that some bird species will nest more than once each year. So you could find a nest in spring and watch the baby birds grow and fly away, only to find another set of eggs soon after.
By the Time They're Gone, the Season Might Be Wrong
Once the nest is abandoned, the birds and bird laws can't prevent you from having the tree trimmed. But if it's summer, that's not the best season in which to trim trees. Cutting now could spur more growth that would only die when colder weather hit later in the year. You'll want to wait until fall or winter when the tree goes into its dormant phase; cutting anything then won't push the tree to suddenly grow more.
Dangerous Limbs Are Usually an Exception
If you need to trim or remove a tree because of damage or because the tree is dying, you may be able to get an exception. However, this requires a number of steps that will be easier for a tree service to handle, rather than handling them yourself. You'll need to have an arborist evaluate the tree; if the tree doesn't appear to be an imminent danger (e.g., it's dying but not about to topple over), you'll likely have to wait for the birds to leave the nest at the end of the season. But if the tree has to come down now because it's this close to falling and damaging a house or harming people, then the tree service should be able to remove the tree. It will need to get federal permission first, though. That's how serious the government is about protecting birds.
If you have a tree that needs work but have also had to deal with a nest in the tree, let a tree service monitor the tree until it's possible to start trimming or removal. It takes patience, but the work can eventually be completed.
For more info about tree services, contact a local company.