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Overview:
Aug 31, 2022: eBird Checklist - Weather Conditions - Surface Archive
Sep 1, 2023: eBird Checklist - Weather Conditions - Surface Archive
Sep 2, 2023: eBird Checklist - Weather Conditions - Surface Archive
This case study starts off as a reasonable example of a fall morning flight at Point Pelee with expected species compositions. This includes many neotropic migrants, which display some "true morning flight" tendencies (e.g., many warbler species), but also some possible fall "onward" migration (Baltimore Oriole?), diurnal migration (Ruby-throated Hummingbird?), and some birds likely leaving nearby roosts (Purple Martin). Things get flipped upside down on September 2 however, with an atypical flight direction (for the location) and also locally atypical composition (see: Swainson's Thrush, Yellow-billed Cuckoo, Common Yellowthroat). There is always more to learn!
Notable Species:
Tennessee Warbler
Key notes: A "true morning flight" species.
Aug 31: 80 - mostly north
Sep 1: 100 - mostly north
Sep 2: 50 - mostly south
Tennessee Warbler are frequently observed in relatively high numbers (fall migration) compared to other species (e.g., Chestnut-sided Warbler, which is common, but never observed in flight in similar relative numbers). Other "true morning flight" species on these days would be Bay-breasted Warbler and Cape May Warbler. Note the flight on Sep 2 involves birds going south, indicating that their direction of flight may be dictated by wind conditions.
Baltimore Oriole
Key notes: Why were so many birds going south on Aug 31 and Sep 1, when most of the "flight" was north? Were they "late" onward migrants?
Aug 31: 16 - roughly 50/50 north and south
Sep 1: 15 - roughly 50/50 north and south
Sep 2: 30 - most south
Nearing the tail-end of their fall migration in Ontario, Baltimore Oriole are regular participants in fall morning flight, but never in the numbers observed locally in spring. This makes for the assumption that the spring flight mechanisms of "adverse weather" or "geographic reorientation" are not at work during the fall, leading to reduced fall numbers due to modest "onward" or "true morning flight" behaviours.
Swainson's Thrush
Key notes: Somewhat rare in flight, the abundant numbers on Sep 1 may indicate some tendencies to undertake true morning flight (?). The volume of the southbound movement on Sep 2 almost defies explanation.
Aug 31: 1 - north
Sep 1: 80 - north
Sep 2: 1400+ - south - short video
Swainson's Thrush are rare but regularly observed in small numbers in southern Ontario during fall morning flight events. The 80 birds represents a larger than average northward movement. These larger movements often coincide with movements of other less-regular or less-abundant species such as Magnolia Warbler or Wilson's Warbler. The 1400+ birds observed on September 2nd, moving south into a south wind, nearly defies explanation. Was there a lack of suitable habitat to the north which encouraged a true morning flight behaviour into the forests of the national park? That might make sense, were it not for the TWO extremley-rare-in-flight Common Yellowthroat also recorded in sustained flight going south (which would surely have noticed the abundant marsh habitats they were flying beside). The most likely explanation may be suitable weather conditions to encourage an "onward" migration that morning.
Yellow-billed Cuckoo
Key notes: perhaps some true morning flight tendencies in fall, yet the justification for a northbound flight on Sep 2 is unknown.
Aug 31: 2 - north
Sep 1: 7 - north
Sep 2: 9 - north
Not dissimilar to Swainson's Thrush as a rare but regular species observed in morning flight, they too decide to defy logic on Sep 2 by continuing to move north - when almost every other species was flying south into the wind. Perhaps their structure and flight style is not influenced by wind to the extent of other species, overridden by another trigger as a desire to move north?
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