|Yellow Warbler on nest. Malheur NWR, Oregon. May 25, 2009 by Greg Gillson.|
A bird on a nest, a bird carrying food to feed to nestlings, very recently fledged young that can't fly far, a bird feigning injury as a distraction display, a blackbird dive-bombing your head. All these are evidence of breeding birds.
As yet eBird doesn't have an output for showing breeding evidence. But that doesn't mean you shouldn't enter such notations. Breeding status may be shown in future update to eBird. However, you can request a download of your data that will show breeding, if you want to investigate your sightings in the future.
Why should you record breeding codes if eBird doesn't output that data yet? Well, for one, observing breeding behavior and searching for nesting evidence is fun! It makes you more aware of what the birds are doing.
For a list of breeding codes and meaning, and for more details, see the eBird page on breeding birds.
Other posts discussing nesting birds.