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Morning Flight
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Rush hour at dawn
It’s almost eerie how punctual birds can be. Along the earthen dike at Higbee
Beach Wildlife Management Area, before the sun crests the horizon, the air is
all or mostly devoid of migrating forms. But as soon as the sun peaks over
the horizon the exodus begins. Through binoculars trained skyward, tiny
sun-spun forms materialize high overhead. In tumbling waves, warblers,
vireos, tanagers and orioles loft out of the trees and zip over, beside and
below the line of waiting observers.
At best you’ll have mere seconds to bring your
binoculars to bear and pin a name to a fast moving form. Even the best get
humbled at “The Dike” and first-timers are sometimes reduced to spectators.
Fifty years ago, the identification of fall
warblers offering ideal and stationary views was considered challenging.
But at the Higbee Dike, the challenges are greater. Here, the birds are
identified in flight using an amalgam of clues--size, shape, overall color or
pattern, manner of flight and (hopefully) vocalizations.
It’s the toughest challenge in
birding. But anybody can play and everyone can marvel at the
number and diversity of birds that constitute the famed "Morning Flight.
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What is "Morning Flight"?
Morning Flight is the directed and often visible movement of migrant songbirds in the first few hours after
sunrise. Most often, this movement occurs during southbound passage and
involves species that typically migrate at night (e.g., warblers, sparrows,
although some diurnal migrants (e.g., Eastern
Kingbird, Northern Flicker) also engage in “morning flight.” During these
events, birds generally move in directions opposite their intended goal (e.g.,
north in fall).
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The discovery of "Morning
Flight"
In the
mid-1970s observers
in both Sweden and the U.S.
began
to document the phenomenon of “morning flight” mainly as it
relates to redetermined migration. Observers suggested that
these events involved the reorientation of birds drifted to
coastal migration sites.
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"Morning Flight" in Cape May
In the mid-1980s, birders at
Higbee Beach Wildlife Management Area (just north of Cape May
Point on the Delaware Bay) noted the early morning
movement of migrant songbirds in fall and this movement was generally
south to north. This was counterintuitive to what might be
expected.
Careful observation eventually
revealed that on days when conditions were favorable for migration, birds could
be seen leaving the last remaining edges of habitat near the Cape May canal and
streaming north; sometimes by the hundreds, thousands, and even
tens-of-thousands.
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Obviously, a phenomenon of such magnitude
invited study. NJAS conducted a two year study of “morning flight” in 1988-89
that resulted in a published manuscript
(Wiedner et al. 1992) in the peer-reviewed ornithological journal, The
Auk. The study documented the morning flight phenomenon in Cape May and
examined several hypotheses proposed to explain morning flight.
Since 2003,
New Jersey Audubon Society’s (NJAS) Cape May Bird Observatory, with support from
Zeiss Sports Optics, has conducted a daily count of the morning flight at
Higbee Beach WMA. The count runs from 15 August to 31 October from atop the
dredge spoil in the northwestern corner of the property, across from the Cape
May-Lewes ferry terminal. To date, nearly one million individuals of 99
species have been recorded during the 2003-2005 field seasons. Two
species, American Robin and Yellow-rumped Warbler make up nearly 80% of all
individuals counted.
Table 1
shows 41 of the most frequently detected species.
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What are the challenges
The accurate
identification of passerines on the wing is a challenge to the observers taking
part in the “Morning Flight” project. The identifications are made in two ways,
by site (1) with high quality optics and (2) by
identifying flight call notes identifying
flight call notes. Sometimes the two methods are used individually; sometimes in
conjunction with one another.
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Proposed
explanations for this unusual phenomenon.
 Forced
migration: Nocturnal migrants are
forced to continue migrating during the day because they are caught over water
or other areas of unsuitable habitat at the time they would be landing.
Migrants could also be forced to continue migration if space or food resources
in a given area are limited.
Redetermined migration: This behavior
is most obvious in coastal areas and thought to result from birds being drifted
off their primary migration course by prevailing winds. Flight direction at a
given location may be strongly influenced by local geography and wind direction.
Movement, usually by nocturnal migrants, is typically in a direction different
from (sometimes opposite) the nocturnal flight path.
Onward migration: Migration by
primarily nocturnal migrants that takes place through the night and into the day
without stopping. Often this is the case in shorebirds and waterfowl, but is a
less widespread phenomenon in songbirds. Flight direction is similar to the
paths followed during nocturnal migration.
Resumed migration: After a
period of rest, nocturnal migrants may resume migration. This movement is
generally limited, mostly to the morning but sometimes can continue well into
the day. Flight direction is similar to the paths followed during nocturnal
migration.
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Table 1. Birds most frequently observed during 2003-2005 field seasons.
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Species |
2,003 |
2,004 |
2,005 |
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Ruby-throated Hummingbird |
61 |
113 |
190 |
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Yellow-bellied Sapsucker |
89 |
84 |
240 |
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Northern Flicker |
4,495 |
1,634 |
5,904 |
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Eastern Phoebe |
23 |
17 |
84 |
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Eastern Kingbird |
2,031 |
1,812 |
3,295 |
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Red-eyed Vireo |
248 |
202 |
379 |
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Red-breasted Nuthatch |
36 |
764 |
455 |
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Golden-crowned Kinglet |
210 |
192 |
662 |
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Ruby-crowned Kinglet |
268 |
189 |
656 |
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Blue-gray Gnatcatcher |
378 |
153 |
392 |
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American Robin |
30,932 |
62,549 |
97,399 |
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American Pipit |
162 |
160 |
278 |
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Cedar Waxwing |
3,861 |
3,982 |
6,774 |
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Tennessee Warbler |
87 |
18 |
37 |
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Nashville Warbler |
79 |
131 |
65 |
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Northern Parula |
1,100 |
736 |
1,523 |
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Yellow Warbler |
157 |
285 |
328 |
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Chestnut-sided Warbler |
36 |
39 |
26 |
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Magnolia Warbler |
73 |
45 |
167 |
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Cape
May Warbler |
305 |
158 |
207 |
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Black-throated Blue Warbler |
667 |
423 |
1,177 |
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Yellow-rumped Warbler |
267,059 |
64,755 |
210,764 |
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Black-throated Green Warbler |
162 |
250 |
179 |
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Blackburnian Warbler |
63 |
27 |
75 |
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Pine
Warbler |
23 |
33 |
23 |
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Prairie Warbler |
17 |
30 |
39 |
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Palm
Warbler |
5,210 |
1,985 |
5,167 |
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Blackpoll Warbler |
1,308 |
973 |
1,721 |
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Black-and-white Warbler |
192 |
239 |
468 |
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American Redstart |
1,755 |
3,011 |
3,482 |
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Northern Waterthrush |
674 |
378 |
681 |
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Scarlet Tanager |
135 |
80 |
151 |
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Chipping Sparrow |
111 |
368 |
3,050 |
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Savannah Sparrow |
98 |
178 |
386 |
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Dark-eyed Junco |
89 |
350 |
3,326 |
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Indigo Bunting |
371 |
233 |
223 |
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Bobolink |
3,747 |
8,099 |
2,230 |
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Eastern Meadowlark |
551 |
321 |
418 |
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Baltimore Oriole |
497 |
928 |
842 |
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Purple Finch |
771 |
974 |
645 |
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Pine
Siskin |
10 |
56 |
23 |
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Copyright © 2009 New Jersey Audubon Society
All rights reserved.
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