Tag Archives: phenology

OSPREY, The Migratory Piscivore

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OSPREY, the Migratory Piscivore

Dr. James J. S. Johnson

While the earth remaineth, seedtime and harvest, and cold and heat, and summer and winter, and day and night shall not cease.

Genesis 8:22

Migrating birds remind me of what God said in Genesis 8:22, about the predictability of annual seasons. It’s really amazing if you think much about it: God selected Moses to report a conversation that God once had with Noah, at the conclusion of the worldwide Flood. In that conversation God promised Noah (and Noah’s family and descendants, which include all of us) that God would not send another global deluge.

OSPREY MIGRATION (The Cornell Lab map, Laura Erickson photo credit)

Rather, day-night periods would continue with constant periodicity, plus weather patterns would be stabilized with predictable patterns, such as the cyclical seasons we know as summer, autumn, winter, and springtime. God’s creatures depend on day-night cycles, as well as on annual cycles–such as the 4 seasons which provide predictability to growing and harvesting food crops (Genesis 8:22, quoted above).

But not only do humans depend upon such phenology patterns, so do animals–especially migratory animals, such as many insects and birds. One such migratory bird is the OSPREY (Pandion haliaetus), also known as the Fish Hawk.

OSPREY (Free Photos and Images photo credit)

Although not all ospreys migrate, most do, according to Donald & Lillian Stokes, A GUIDE TO BIRD BEHAVIOR, volume III (Boston: Little Brown & Company,1989 ), pages 169-170. In fact, most ospreys of North America–such as those of the Chesapeake Bay region–are known for over-wintering in or near South America, regularly returning to North American ranges during spring:

The warmer temperatures have brought with them a familiar Chesapeake icon. Ospreys (Pandion haliaetus) occur in nearly every corner of the globe, but nowhere as abundantly as on the Chesapeake Bay.

Ospreys return to the Chesapeake every spring from southern wintering grounds. Their abundance in the Bay region is due to the availability of food: They feed exclusively on live fish.

Their curved, sharp talons and rough-soled feet are designed to hold on to slippery fish.

Large brown and white birds of prey, they’re about 2 feet long with wing spans of 4-5 feet. When in flight, their long, narrow wings take on the shape of an outstretched M.

Ospreys hunt by soaring over water, periodically hovering on beating wings to scan the surface for schooling or spawning fish. Upon sight of its prey, the osprey makes a spectacular dive. Folding its wings tightly, it descends swiftly and plunges feet first into the water, often submerging itself completely. Another technique is a shallow scoop for fish at the water’s surface.

In addition to food, the Chesapeake provides many favorable nesting areas over the water such as duck blinds, navigation markers or man-made nesting platforms. Offshore structures offer protection from predators like raccoons, and rapid detection and escape from danger. On land, ospreys may nest on high trees and utility poles.

Ospreys 3 years or older usually mate for life, and will use the same nest site year after year A recently reunited pair will begin the task of nest building or repair.

Kathy Reshetiloff, “Chesapeake’s Ospreys Mark Return of Spring”, CHESAPEAKE BAY JOURNAL (June 19th, A.D.2020).
OSPREY (PublicDomainPictures.net photo credit)

Thanks for that report, Kathy Reshetiloff–that report that repeatedly fits the return of spring. This year (A.D.2022) is no exception, according to a short report in the CHESAPEAKE BAY JOURNAL:

Standing watch over a channel marker, soaring above the water, effortlessly snatching a fish — ospreys are among the most recognizable bird species in the Chesapeake Bay region. And they have begun their annual springtime return from South America.

Staff writer, “A Sign of Spring: The Return of the Chesapeake’s Ospreys”, CHESAPEAKE BAY JOURNAL, 32(2):3 (April 2022).

The Osprey is a daytime-hunting raptor, like others hawks and eagles, seizing its prey after a successful chase. And for the Osprey, that hapless prey is most likely fish of some kind–more than 99% of the Osprey’s diet is some kind of fish!

OSPREY (PublicDomainPictures.net photo credit)

However, according to the University of Michigan’s Museum of Zoology website “Animal Diversity Web” [ AnimalDiversity.org entry for Pandion haliaetus ], an extra-hungry Osprey might catch and consume rodents (mice, rats, voles, squirrels), lagomorphs (rabbits, hares, pikas), small birds, salamanders, snakes, juvenile alligator, or even carrion (e.g., dead opossum, deer carcass). But those are rare dietary choices for an Osprey, because they have earned their common nickname, “Fish Hawk”.

Ospreys are not bashful about seizing fish prey, whether those prey are near the water’s surface or whether such prey is well below the water’s surface.

[The Osprey] is the only raptor that plunges into water feet first to catch fish. Can hover for a few seconds before diving. Carries fish in a head-first position for better aerodynamics [for post-catch flying]. Often harassed by Bald Eagles for its catch.

Stan Tekiela, BIRDS OF TEXAS FIELD GUIDE (Adventures Publications, 2004), page 79.

Hmm. that last “kleptoparasitism” fact–about eagles robbing ospreys of caught fish–where did I read about that recently? Oh yeah, I saw something about that on the best birdwatching blog in the world, LEESBIRD.COM — https://leesbird.com/2022/05/17/a-fisherman-robbed-chapter-20/ .

Kleptoparasitic Eagle chasing Osprey with fish (CenteroftheWest.org photo credit)

It pays to be a regular reader of LEESBIRD.COM ! — thanks, Mrs. Lee Dusing, for the ongoing blessing your birding blog has been, for years, is now, and continues (God willing) to be. (And thanks also for your sterling service as an Adjunct Professor to ICR’s School of Biblical Apologetics, over the past few years.) But mostly, thanks for honoring the Lord Jesus Christ, (our Creator-Redeemer) and for continually blessing birdwatchers, like me, with the wonderful service that LEESBIRD.COM provides. : )

OSPREY featured on heraldic Coat-of-arms of Sääksmäki, Western Finland (public domain)

CLIFF SWALLOWS: Faithful as Mates, Migrants, and Mud-home Masons

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CLIFF  SWALLOWS:  FAITHFUL  AS   MATES,  MIGRANTS,  AND  MUD-MASONS

Dr. James J. S. Johnson

Thine own friend, and thy father’s friend, forsake not; neither go into thy brother’s house in the day of thy calamity: for better is a neighbor that is near than a brother far off.  (Proverbs 27:10)

Alongside a rocky hillside outcropping, or under a montane cliff overhang, the mud-home “condominiums” of the Cliff Swallow (Petrochelidon pyrrhonota) reveal the presence of this gregarious and aerial-acrobatic bug-eater.

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CLIFF SWALLOW inside mud-nest

National Park Service photo / public domain

On June 29th of AD1996, by Colter Bay Village Marina, in Grand Tetons National Park (Wyoming), I saw some of these, and considered how their colonial nests reminded me of the riparian (i.e., riverbank) Bank Swallow (Riparia riparia) burrows that I had seen (2 days earlier) along banks of the Snake River.

Like other swallows, the Cliff Swallow speedily zips and arcs and dives through the air, snatching and consuming many “meals on wings” – veritable “fast food” – gulping down airborne insects, again and again.  (The Cliff Swallow supplements its insectivorous diet with berries and other fruits.)

However, the Cliff Swallow’s claim to fame is their colonial mud-home masonry.

“Hundreds of gourd-shaped “mud jugs” plastered to the side of a barn or under a bridge or highway overpass are a typical [colonial] nesting territory for these highly adaptable birds. Farmers heartily welcome this [summer] resident because it eats numerous flying insects that are harmful to crops. Nesting colonies may number from 800 to more than 1,000 birds. Note the dark rusty brown throat, and in flight the brown underwing linings, cinnamon buff rump, [characteristic] square tail, dusky cinnamon undertail coverts with dark centers, and whitish buff edged feathers of back and tertials. Juveniles have dusky brown upperparts and paler underparts. This [bluish-brown-black-backed] swallow has successfully expanded its range in the [American] Southwest and the West. The southwestern race [i.e., variety] displays a cinnamon forehead similar to the Cave Swallow.”

[Quoting Frederick J. Alsop III, BIRDS OF TEXAS (Smithsonian Handbooks, 2002), page 363.]  Cliff Swallows closely resemble Cave Swallows (Petrochelidon fulca), but Cave Swallows have a “pale cinnamon-buff throat”, cinnamon-rust-hued throat, and a “richer cinnamon-rust rump”, according to Alsop [at page 363].  Another similar-looking swallow is the deeply-forked-tailed Barn Swallow (Hirundo rustica) which often colonizes the inside of rural barns (as well as in places where Cliff Swallows build nests) all over America’s Lower 48 states.

In fact, these 3 varieties of swallows — Cliff Swallow, Cave Swallow, and Barn Swallow – are known to hybridize, so there is no need to fret over which species name you assign to one of these swallows.   [For documented examples of these mud-homebuilding swallow hybridizations, as well as many other swallow and martin hybridizations, see Dr. Eugene M. McCarthy’s HANDBOOK OF AVIAN HYBRIDS OF THE WORLD (Oxford University Press, 2006), pages 253-255.]

Other forms of “hybrid” mixing occur, involving other types of social interaction, such as the neighborliness known as “helping”:

“NEST HELPERS occur among many species, including certain kingfishers, hawks, jays, tanagers, and wrens. Helpers are generally younger adults that assist their parents in rearing nestlings. . . . Helpers generally do all of the usual nest-associated behaviors, such as building nests, incubating eggs, guarding nestlings, cleaning the nest, and feeding young. With such help, it’s not surprising that several studies have shown that [parental] pairs with nest helpers can rear more young than those without helpers. . . . While most helpers assist their parents [with the care of younger siblings], there are also many examples of adults feeding young of different species. Parent Barn Swallows may, for example, feed fledgling Cliff Swallows. Robins have been known to feed young grackles.”

[Quoting Stephen W. Kress, BIRD LIFE: A GUIDE TO THE BEHAVIOR AND BIOLOGY OF BIRDS (Racine:  Golden Press, 1991), page 54, with emphasis added.]

CliffSwallow-nesting.WhatWhenHow

CLIFF SWALLOW on mud-home nest

Photo credit: What-When-How.com Tutorials

The Cliff Swallow takes all of its social relationships seriously – they are characteristically monogamous, sometimes rearing 2 broods in one breeding season, and they live gregariously in large colonies. [See Stan Tekiela, BIRDS OF TEXAS FIELD GUIDE (Adventure Publications, 2004), page 125.]  Also, they share information about where to get food.  When some of these swallows observe other fellow-colonist swallows returning with food for their young, indicating the successful sourcing of food, those watching follow suit, following the “winners” to the place where food is readily available.

Professor Alsop describes the Cliff Swallow’s homebuilding hallmark as the construction of “one of the most complex swallow nests: a sphere of mud pellets with a tubular entrance on one side”.  [Quoting Alsop, BIRDS OF TEXAS, cited above, page 363.]  Unsurprisingly, Cliff Swallow nesting colonies are located near water, since water is needed by both the swallows and their insect prey.  Little mud-balls used for nest-building, carried serially during nest construction, may be acquired from mud sources a mile away.

CliffSwallows-getting-mud.CameronRognan

CLIFF SWALLOWS acquiring mud for nest-building

Photo credit: Cameron Rognan / Flickr

These swallows migrate, breeding all over Texas, often returning each spring to last year’s nesting sites. In fact, Cliff Sparrow migratory punctuality is famous:

“THE TIMING OF MIGRATION is [phenologically] linked to the length of day [i.e., daylight hours]. As day-length increases with the advancing spring [season], birds develop a nocturnal restlessness called “zugunruhe” [from 2 German words meaning move/migration and anxiety/restlessness]. Increased exposure to daylight leads males and females to higher hormone levels that trigger the urge to migrate [northward from South America]. Migration becomes a predictable event. Cliff Swallows of San Juan Capistrano Mission in southern California and Turkey Vultures of Hinkley, Ohio [not to be confused with Hinckley, Minnesota – “where the men are men, pansies are flowers, and the women are slightly above average”] , are noted for their punctual spring arrivals. The spring arrivals of many backyard birds, such as American Robins and Red-winged Blackbirds are equally punctual.”

[Quoting Stephen W. Kress, BIRD LIFE: A GUIDE TO THE BEHAVIOR AND BIOLOGY OF BIRDS (Racine:  Golden Press, 1991), page 108.  Regarding zugunruhe and photoperiod analysis, see Eberhard Gwinner, “Circannual Rhythms in Bird Migration”, Annual Review of Ecology & Systematics, 8(1):381-404 (1977), posted at http://www.annualreviews.org/doi/10.1146/annurev.es.08.110177.002121 — with an acknowledgement that “internal annual clocks” had been demonstrated earlier in hibernating Golden-mantled Ground Squirrels.]

Like other swallows, the Cliff Swallow speedily eats many “meals on wings”  –  veritable “fast food”  –  catching and eating insects in the air.  The Cliff Swallow supplements its insectivorous diet with berries and other fruits.

Thus, the Cliff Swallow is faithful in mating (i.e., avian “marriage” and parenting), faithful in migrating (i.e., in the phenological punctuality of its spring migrations), and faithful in its mud-home masonry tradition. Cliff Swallows are famous for sharing and living together in harmony – like good neighbors.

><> JJSJ   profjjsj@aol.com

Shorebirds Looney about Horseshoe Crab Eggs

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RedKnot-DelawareBay-beach.GregoryBreese-USFWS

Red Knot Eating Crab Eggs at Delaware Bay Beach

Photo by Gregory Breese / USF&WS

Thankfully, the rhythms of our world are fairly predictable. Although the details differ, the overall cycles are regular:

While the earth remains, seedtimes and harvest, and cold and heat, and summer and winter, and day and night shall not cease. (Genesis 8:22)

Because of these recurring patterns migratory birds can depend on food being conveniently available when they migrate northward in the spring. In effect,  “fast food” on the beach is a “convenience store” for famished feathered fliers.

For example, consider how the annual egg-laying (and egg-burying) activities of horseshoe crabs perfectly synchronize with the hunger of migratory shorebirds (e.g., red knots, turnstones, and sandpipers) that stopover on bayside beaches, for “fast food”, right where huge piles of crab eggs have just been deposited (and where some have been uncovered by tidewaters).

HorseshoeCrabs-DelawareBay-beach.GregoryBreese-USFWS

Horseshoe Crabs on Delaware Bay Beach

Photo by Gregory Breese / USF&WS

No need to worry about the birds eating too many crab eggs! – the egg-laying is so prolific (i.e., about 100,000 eggs per mother) that many horseshoe crab eggs are missed by the migratory birds, thus becoming the next generation of horseshoe crabs, plus the birds mostly eat the prematurely  surfacing eggs that are less likely to succeed in life anyway!)

Timing is everything. Each spring, shorebirds migrate from wintering grounds in South America to breeding grounds in the Arctic. These birds have some of the longest migrations known. Delaware Bay is the prime stopover site and the birds’ stop coincides with horseshoe crab spawning. Shorebirds like the red knot, ruddy turnstone and semipalmated sandpiper, as well as many others, rely on horseshoe crab eggs to replenish their energy reserves before heading to their Arctic nesting grounds.  The birds arrive in the Arctic before insects emerge. This means that they must leave Delaware Bay with enough energy reserves to make the trip to the Arctic and survive without food until well after they have laid their eggs. If they have not accumulated enough fat reserves at the bay, they may not be able to breed.

The world’s largest spawning population of horseshoe crabs occurs in Delaware Bay. During high tide, horseshoe crabs migrate from deep water to beaches to spawn. The female digs a nest in the sand and deposits between 4,000 and 30,000 eggs that the male will fertilize with sperm. A single crab may lay 100,000 eggs or more during a season. Horseshoe crab spawning begins in late April and runs through mid-August, although peak spawning in the mid-Atlantic takes place May 1 through the first week of June.

At low tide, adult crabs go back into the water but may return at the next high tide. Horseshoe crab spawning increases on nights with a full or new moon, when gravity is stronger and high tides are even higher. At the same time that migrating shorebirds arrive to rest and feed along Delaware Bay, horseshoe crab activity is high. While the crab buries its eggs deeper than shorebirds can reach, waves and other horseshoe crabs expose large numbers of eggs. These surface eggs will not survive, but they provide food for many animals. The shorebirds can easily feed on eggs that have surfaced prematurely.

Quoting Kathy Reshetiloff, “Migratory Birds Shore Up Appetites on Horseshoe Crab Eggs”, THE CHESAPEAKE BAY JOURNAL, 27(3):40 (May 2017).

Shorebirds-HorseshoeCrabs-DelawareBay.LarryNiles

Shorebirds and Horseshoe Crabs on Delaware Bay Beach

Photo by Larry Niles

Notice how it is the gravitational pull of the moon, as the moon goes through its periodic cycle, that causes the high and low tides – which facilitate the uncovering of enough horseshoe crab eggs to satisfy the needs of the migratory stopover shorebirds that pass through Delaware Bay.  Notice how the moon provides a phenological “regulation” (i.e., the moon is physically ruling and correlating the interaction of the horseshoe crabs, the migratory shorebirds, and the bay’s tidewaters – in accordance with and illustrating Genesis 1:16-18).

At low tide, adult crabs go back into the water but may return at the next high tide. Horseshoe crab spawning increases on nights with a full or new moon, when gravity is stronger and high tides are even higher. At the same time that migrating shorebirds arrive to rest and feed along Delaware Bay, horseshoe crab activity is high.

Again quoting Kathy Reshetiloff, “Migratory Birds Shore Up Appetites on Horseshoe Crab Eggs”, THE CHESAPEAKE BAY JOURNAL, 27(3):40 (May 2017).

RedKnot-MigrationMap.NatureConservancy
Map of Red Knot Winter Ranges, Summer Breeding Range, & Migratory Stopovers
Map by The Nature Conservancy, adapted from USF&WS map

So, you might say that these reproducing Horseshoe Crabs, and the myriads of migratory shorebirds, share phenological calendars because they’re all looney.

RedKnot-onshore.NatureConservancy-MJKilpatrick

Red Knot on Beach, during Migratory Stopover
photo by The Nature Conservancy / M J Kilpatrick