Soon afterward, I would hear a Vesper Sparrow singing on territory and a few hundred yards was another. At the edge of a grassy area a Grasshopper Sparrow was singing and teed up on a sign post. There is great Grasshopper Sparrow habitat nearby, on the Devens military base (South Post), which is an active training area, fortunately at least a few Grasshopper Sparrows have defected to civilian territories. This bird had a metal band on its left leg, though no numbers could be read.
Arriving at Bolton Flats at 6AM, two American Bitterns could be heard calling and the spring shorebird show was nice with 9 species present including Killdeer (10+), Greater (18) and Lesser Yellowlegs (5), Solitary (15), Spotted (5), Least (2), Pectoral Sandpipers (3), Dunlin (4) and Wilson's Snipe (8).
On the Marsh bird side of the equation, in addition to the bitterns was a Virgina Rail, in full view and two Marsh Wrens. I did not hear the previously reported Sora, but the two Green Herons flying overhead were my first of the year.
Yellow Warbler ...12
Northern Parula ...7
Chestnut-sided ...Warbler 1
Pine Warbler ...2
Blackburnian Warbler ...1
Yellow-rumped Warbler ...20+
Blackpoll Warbler ...1
Black and White Warbler ...7
American Redstart ...4
Ovenbird ...5
Common Yellowthroat ...15