As with the rest of the world, 2020 was a challenging but still productive year at GMI. Monthly socially distanced public bird walks continued but with limited turnout due to COVID-19. A total of 151 species were observed or remotely recorded this past year; up from 133 species in 2019. A total of four new species were recorded: Mute Swan (March 15th), Horned Grebe (April 11th), Semipalmated Plover (May 15th), and Olive-sided Flycatcher (August 30th). These additions bring the total number of species seen to 187 which continues to rank GMI in the 10th spot for eBird hotspots in Chester County.
Spring Migration (Mar-May)
The Spring Migration period had a total of 120 species reported which was an increase by one from 2019. 2020 was the first year in which we deployed recording devices in several areas of the marsh in order to capture some of the more elusive species this unique area hosts. On the evening of March 21st at 7:07PM, a group of Sandhill Cranes were recorded coming in to rest for the evening and then at 6:59AM the next morning they were recording taking off and exiting the property. This is the third time that this species has been recorded/observed in migration here. Four birds were seen on March 24th in 2013 and one bird was seen on April 21st, 2018. It now appears likely that GMI is an important stopover for this species in spring migration. It will be interesting to see if they are recorded once again in the 2021 recording campaign.
Blue-winged Teal were once again seen migrating through in April. A Mute Swan was recording in March and a Horned Grebe was recorded in April; both new for the property. Virginia rail were recorded singing throughout the Marsh starting in March. An apparent decline in Sora was noted in the recordings and should be more closely monitored this year. There was only one recording of American Kestrel during this period. There are two Kestrel boxes installed and we are hoping again that this year we can attract a pair. Other species of note include: Black-billed Cuckoo, Semipalmated Plover, Glossy Ibis, Barred Owl, and Horned Lark.
The beginning of Winter (December) saw 48 species recorded; 3 more than the previous year. Continuing with the winter invasion, a Black-capped Chickadee was observed along with continued Purple Finches and Pine Siskins.
Winter Season (Jan-Feb)
The Winter season came in with a count of 50 species, seven greater than the previous year. Great Marsh continued to host a wintering population of Rusty Blackbirds which are rare in Eastern Pennsylvania. Total populations of Rusty Blackbird have declined 85%-95% in the period between 1970-2010. Great Marsh has the unique habitat necessary to host wintering populations and favored areas include the NW sector of the Catfish pond and adjacent thickets and the wet woodlands south of the Spring pond. Other species of note include: American Kestrel, Eastern Phoebe, Fox Sparrow, and White-crowned Sparrow. Once again, a notable absence was a lack of Long-eared Owls of which wintering populations have been recorded annually. Habitat improvement efforts involving the planting of a new White Pine grove are planned for this year to sustain this species in the future.
Breeding Period (Jun-Jul)
The Breeding Period had a total of 66 species recorded; the same number as last year. There were four species recorded that were different from last year: Cooper’s Hawk (nested in the Pine Grove), American Kestrel (assumed to be nesting in the area, but not on GMI property), Warbling Vireo (assumed breeder along the creek), and Orchard Oriole (assumed breeder). The Great-blue Heron rookery continued in the lower marsh. Of special note, several electronically tagged Purple Martins were detected via the GMI MOTUS receiver. This was very encouraging and prompted GMI to apply for and receive a grant from the Purple Martin Conservation Association. We will be installing two purple martin housing units this spring in an attempt to establish a breeding colony on the property.
Fall Migration (Aug-Nov)
Fall Migration hosted a count of 117 species; significantly up from a count of 91 in the previous year. This is most likely due to better coverage in the upland woods between Rt 401 and the creek. This area is the best place to spot migrating warblers, flycatchers, etc. A post-breeding Great Egret once again took up residence from the first week in August into the first week of September. An Olive-sided Flycatcher was seen on August 30th and was a new species for the property. This species appeared to have an irruption year as several were spotted around the county. Blue-winged Teal stopped over on their migration south in good numbers. A March Wren was observed on October 1st. This is a species of special interest and more effort to needs to be put forth in the coming year to better understand their presence here. Several Lincoln’s Sparrows were sited along with a pair of Vesper Sparrows. Fall 2020 into Winter 2021 appears to be an invasion year for northern birds due to lower food supplies in Canada. This is a normal cyclical event species recorded include: Purple Finch, Red-breasted Nuthatch, and Pine Siskin.