They seemed to be taking whole reeds, perhaps to line their nests in the rocks. Rats can be awfully finicky about their nests. 
Rattus rattus, baby. Updated: Evidently actually Rattus norvegicus. See comments.
In the Spartina
Published October 22, 2013 Fieldnotes 11 CommentsTags: Brooklyn, Brooklyn Bridge Park, mammals
Backyard and Beyond 
Urban chipmunks.
You make the rats look cute.
These look like the field mice that climb wildflowers in South Dakota.
Love all your photos of nature.
Don’t you mean norvegicus?
I thought R. rattus with those big ears and eyes, the long tails, and the lighter underside, but I’m no expert by any means. What makes you think R. norvegicus?
Rattus rattus is the black rat – more likely in ships and rooftops. I’m pretty sure these are the Norway rat – they look like the others we see around town. We don’t have that many black rats around here, from what I understand.
Crouching Tiger, Hidden Dragon?
The black rat does come in a range of colors. Anyway, it’s definitely Rattus somethingorother.
R. norvegicus comes in different colors too – you should see the variety of domestic “fancy” rats that have been developed from them. Queen Victoria’s official (!) rat catcher used to keep and breed the odd ones he found.
But either species is remarkably appealing – at least to me. I’ve only met one black rat – one that my nephew-in-law and I had to remove from their bathroom in Mill Valley, CA. Poor little thing was terrified – first by being cornered by their cat, then by our trapping her. When we took her out and released her in the woods, I’m sure she had learned her lesson about entering human dwellings.
I don’t think R. rattus occurs here.
I checked with Robert Sullivan, author of Rats, and he concurs on R. norvegicus. Thanks for the sharp eyes, JMR and Elizabeth.