Hi Laura!
One possible explanation is that at this time of year birds have high reproductive hormone levels.  Some females are capable of producing eggs without being fertilized, much like chickens do.  These unfertilized shelled eggs are extra weight that a bird does not want to carry around, so she "dropped" the egg prior to flight so that she would be lighter.  You'll also notice many birds defecate prior to lifting off.  This is also so they are not carrying extraneous weight during flight.
The downside of shedding unfertilized eggs is that it puts a strain on the female for calcium.  The shells are produced with calcium from the bones of the female bird, or rather a particular layer of bone called the medullary bone.  It's important that female birds replace the calcium they lose from their bones through dietary sources; primarily invertebrates and sometimes discarded eggshells. 
Hope this helps!
Casey

> Date: Sun, 19 Apr 2015 02:14:52 +0000
> From: [log in to unmask]
> Subject: Re: [Ohio-birds] robin dumping egg
> To: [log in to unmask]
> 
> I think I need to clarify about the robin that  dumped an egg an egg onto the ground.  She was NOT carrying the egg in her beak; she raised her tail and the egg came from her body.  I watched her land on the branch--she had nothing in her mouth.  I know this specifically because I was hearing a robin singing and I looked to see if it might be her.  It was not, her beak was shut.   She was only 20 to 30 feet from me and I was watching her through binoculars.  She definitely "laid" the egg herself, there just wasn't a nest there for her to deposit it in.  When I went to take a closer look (I could hardly believe I saw what I knew I saw), it was definitely a robin egg with very fresh yolk (I have seen lots of robin eggs, a robin would nest on our front porch almost every year for about 20 years or more).
> So any thoughts on birds laying eggs where there is no nest or even anything solid underneath them?
> Laura DornanLouisville
> 
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