Category Archives: Tenth Page


After a week near western gulls in San Diego I got pretty used to seeing individual gulls perched high, watching the others fly by.  Inevitably, the lone gull would throw his head back and give the long call when other gulls flew over. What did he mean?

The "long call" is used in many contexts, as a greeting between mates or a statement about territory.  In this video two great black-backed gulls give the long call when they fight over a fish.  Watch the video and I'll tell you what I think about their interactions.

Their gestures tell the tale.

  • The hungry gull (HG) approaches, bowed low in a threatening gesture.
  • The eating gull (EG) sees the threat and opens his wings, "Back off!"
  • HG turns away and gives the Long Call:  He hunches over, bows his head, then lifts it high leaning his body at an oblique angle and calling loudly.  You might think he's not talking to EG because he's not looking at him.  Far from it!  By turning away he's avoiding direct confrontation.  Perhaps he's trying appeasement.
  • That didn't work.  HG walks past EG without looking at him directly.  As he approaches EG's tail he gets an idea.
  • Tail pulling didn't work at all, so the hungry gull bows low (a threat) and walks to the front of EG.  Facing him and opening his wings (again, a threat), he tries to steal the fish.
  • Finally the eating gull has had enough.  The two fight.  EG quickly wins.  Hungry Gull retreats while EG gives the long call in triumph, and then resumes his meal.

What's the relative stature of these gulls?  My guess is that EG (the eating gull) outranks HG (hungry gull), but HG is willing to test the limits.


(Video by littleW007 on YouTube. Today’s Tenth Page is inspired by page 320 of Ornithology by Frank B. Gill.)

The Cheapest Way To Go

Golden-winged sunbird (photo from Wikimedia Commons)

In Africa sunbirds fill the ecological niche that hummingbirds fill here.  Like hummingbirds, they feed on nectar, have long down-curved bills and come in beautiful iridescent colors.  The main difference is that sunbirds perch instead of hover.

Like hummingbirds, sunbirds also pugnaciously defend their nectar sources and spend a lot of time chasing and fighting.  What is the advantage in doing this?  Doesn't it cost more energy than peaceable feeding?

In 1975 Gill and Wolf studied the energy expended by territorial golden-winged sunbirds in Kenya.  Their results were a bit surprising.  It costs less energy per day to defend really good nectar sources than it does to feed at undefended low-nectar flowers.

Here's the math:

  • Undefended flowers have less nectar because so many birds are feeding at them.  Foraging burns 4 kilojoules of energy per hour but it takes 8 hours to get enough food.  8 hours * 4 kilojoules/hour = 32 kilojoules burned.
  • Defended flowers have twice as much nectar so it takes only 4 hours to get the same energy.  4 hours * 4 kilojoules/hour = 16 kilojoules burned while foraging.
  • Defending these flowers is energy intensive (12.5 kilojoules/hour) but if it doesn't take much time it's worth it.  If it only takes 20 minutes to defend those flowers in that same 8 hour period the results are:   0.33 hour * 12.5 kilojoules/hour = 3.7 kilojoules burned in defense.
  • What does a territorial sunbird do with all that extra time?  He sits around and watches his flowers.  3.7 hours * 1.7 kilojoules/hour = 6.3 kilojoules spent sitting.
  • Therefore his total energy expenditure is 26 kilojoules, a savings of 6 kilojoules in 8 hours.

That's why hummingbirds are so belligerent at our feeders.  They're making the calculation that defending a great food source is the cheapest way to go.

Photo of a golden-winged sunbird from Wikimedia Commons.  Click on the image to see the original.
Today’s Tenth Page is inspired by page 310 of Ornithology by Frank B. Gill.

What Color Is A Scarlet Ibis…Really?

What color is a scarlet ibis? (original photo by tj on Wikimedia Commons)

The scarlet ibis looks bright orange-red to us but that's not what the ibis sees.

Unlike humans, birds can see ultraviolet light.  This trait was discovered by accident and largely ignored until we figured out that most birds have ultraviolet-reflectant feathers.   This opened up a whole new view of plumage.

Above is my poor attempt at showing what this looks like.  Instead of orange-red the ibis appears purplish to himself and other birds -- more purple than I can show.  For an awesome photo of what birds actually look like click here and scroll down to see three views of a cockatiel.

When the ultraviolet colors came to light we uncovered many surprises.  The axillary feathers of northern saw-whet owls are UV-reflectant. Who knew their armpits were so flashy!  The brightness fades in older feathers so bird banders use UV light to age the owls.  Here's a saw-whet UV photo linked from Washington College's Chester River Field Research Center where they band the owls.  (Click on the photo to read more.)

The world of birds is far more colorful than we imagine.

A scarlet ibis does not look scarlet to an ibis.  Really.


Scarlet ibis photo by tj on Wikimedia Commons, retouched by Kate St. John to attempt ultraviolet shades. Click on the image to see the original.
Northern saw-whet UV axillary feathering by Washington College, Chesterfield River Research Center, Northern saw-whet monitoring.
Today’s Tenth Page is inspired by page 100 of Ornithology by Frank B. Gill.

Bigger Is Better In Winter

Male House Sparrow (phot by David Lofink via Wikimedia Commons)

Much as we're unhappy with the results, the introduction of house sparrows from Europe began a grand experiment in avian adaptation.

House sparrows were introduced to both the U.S. and New Zealand in the 1850s where they immediately became isolated from their native populations.  More than 150 years later they differ based on where they live.

In addition to changes in plumage the birds are different sizes.  In locations where winters are harsh, the birds are large.  Where the climate is moderate, they are smaller.  This effect is called Bergmann's rule and is true of birds around the world.

In 1992 William A. Buttermer studied house sparrows at a winter roost in Ann Arbor, Michigan where he found that the largest males survived the best.

Not only were the large birds able to thermoregulate better than the small ones but they had two other advantages.  The larger birds claimed the most favored roosts and they were able to fast longer.

During winter storms birds must roost and wait for the weather to improve, so they are forced to fast.  The larger birds survived fasting better than small ones.

It's better to be bigger in winter.

(photo by David Lofink via Wikimedia Commons.  Click on the image to see the original.  Tenth Page is a "wild card" inspired by page 161 of Ornithology by Frank B. Gill.)

Extinction By Rabbit

Laysan Rail (drawing by Walter Rothschild from Wikimedia Commons)

On Monday I wrote about cats and windmills as threats to bird life but neither of them are the leading reason why birds die.  The number one cause of bird death worldwide is habitat loss.

The Laysan rail (Porzana palmeri), pictured above, went extinct in the 20th century because of habitat loss with a bizarre twist.

Laysan is a small, isolated island in the middle of the Northwestern Hawaiian Island chain.  Only 1 by 1.5 miles across its land area is 1,016 acres, about twice the size of Schenley Park.

Laysan is famous for its bird life, a nesting island for many Pacific seabirds and home of the rare Laysan albatross and even rarer Laysan duck.  It was also the home of the Laysan rail, a fearless, flightless bird less than 6 inches long.

Unfortunately, in 1903 Max Schlemmer released rabbits on the island as a money-making venture.  Instead of making money it was the beginning of the end.  The rabbits on Laysan had no predators and in short order they overran the island.  (Keep in mind that a rabbit can bear 35 young per year.)  The rabbits ate everything.  Everything.

By 1918 Laysan was a barren dustbowl on which only 100 rabbits survived.  With little to eat and no cover the Laysan rail population was hanging on by a thread.  Meanwhile a few rails had been introduced to other islands in the northwestern Hawaiian chain in hopes they could survive elsewhere.

In 1923 the Tanager Expedition eradicated Laysan's rabbits but it was too late for the rail.  The last two on the island died that year.  A few hung on at other islands in the chain but the final blow fell in 1944 when a World War II ship drifted to shore on Eastern Island, Midway and the ship's rats swam ashore.  The rats ate the last Laysan rails on earth. That was that.  Extinction.

In the broadest sense, loss of habitat killed the Laysan rail.  In a narrow sense it was a case of extinction by rabbit.

(drawing by Walter Rothschild from Wikimedia Commons. Click on the image to see the original.  Today's Tenth Page is inspired by page 640 of Ornithology by Frank B. Gill.)

Slots Help Me Fly

Turkey vulture (photo by Chuck Tague)

A bird's lifestyle is written in its wings.

Birds who fly fast and maneuver quickly, such as peregrines and swifts, have narrow pointy wings built for speed and agility.  They need this equipment to capture prey in the air.

Birds who soar slowly in search of food, such as red-tailed hawks and turkey vultures, have broad wings with a lot of surface area.

Broad, blunt wings create a lot of wingtip turbulence (remember those vortices?) so soaring birds have feather slots at their wingtips.  This confers two flight advantages.

First, each feather stands alone like a tiny pointy wing with a high aspect ratio (ratio of length to breadth) that's more like a peregrine's wing.   The winglets create less turbulence and therefore less drag.

The second advantage is in the gaps. As air is forced upward between the feather slots, it expands on the upper side creating low air pressure on top and therefore more lift.

Turkey vultures are masters of slow speed flight.  They turn and teeter without flapping -- not even once!

The slots help them fly.


(Photo by Chuck Tague.  Today's Tenth Page is inspired by page 120 of Ornithology by Frank B. Gill.)

Fanciful Eggs

We see chicken eggs every day so we tend to assume all eggs are plain and never shiny.  In reality most eggs are not.

Shown above is an illustration of 50 European bird eggs by Adolphe Millot published 1897-1904(*).

The eggs have many shapes and sizes from the goldcrest's tiny pink oval (#19) to the large pointed pyriform egg of the now extinct great auk (#47).

Few are a single solid color but even those are amazing -- from pink to robin's-egg blue to a beautiful avocado color.  Tinamous are from South America so their eggs aren't pictured here, but it's worth clicking this link to see their glossy eggs in several colors.

The dark patterns on eggs are almost fanciful wreaths, caps, scrawls, dots, streaks and blotches.  They're made by protoporphyrin which is deposited within or on the shell while in the bird's uterus.  These dark spots are stronger than the plain calcium shell and tend to be deposited where the eggshell is thinnest.  Some birds lay on extra protoporphyrin when their personal calcium supplies are low.

And, as a final touch some eggs are shiny, some are waterproof.  I have read that duck eggs feel oily and that jacanas, who build floating nests, lay eggs that are lacquered (#29, in the top row).

Explore the eggs in the illustration using the quick key below.  If you click on the image you can zoom the original to read the egg numbers.

Illustration of European bird eggs from "ŒUFS" (Eggs) by Adolphe Millot from Nouveau Larousse Illustré [1897-1904], in the public domain via Wikimedia Commons.  (*) This image has been altered as described in the "p.s." below.  Click on the image to see the original.

Inspiration for this Tenth Page is from an illustration on page 400 of Ornithology by Frank B. Gill.)

p.s.  Key to the illustration, copied from Wikimedia Commons:
The original French designation may not correspond to the modern French term. Eggs 1-50 are bird eggs, reduced in size by about a third.  Eggs 51-72, (*)which I erased from this illustration, were from turtles, reptiles, moths etc. I erased them to highlight only the bird eggs.  Click on the image above to see the complete original on Wikimedia Commons.

#    French        English
1    De bondree    honey buzzard (?)
2    De faucon    falcon (?)
3    D'epervier    Eurasian sparrow-hawk
4    De merle    blackbird
5    De grive    thrush
6    De freux    rook
7    De bruant proyer    corn bunting
8    De gros-bec    hawfinch (or perhaps another grosbeak?)
9    De moineau    sparrow
10    De pinson    chaffinch (or other finch?)
11    De pitpit    pipit
12    De bruant des roseaux    reed bunting
13    De coucou    cuckoo
14    De petit oiseau-mouche    hummingbird (?)
15    De bec-croise    crossbill
16    De troglodyte    wren
17    De sittelle    nuthatch
18    De rossignol    nightingale
19    De roitelet    Kinglet (Goldcrest?)
20    D'accenteur    accentor
21    De bruant fou    rock bunting
22    D'effarvate    reed warbler
23    De rousserolle    sedge warbler (or other Acrocephalus?)
24    De fauvette    warbler (??)
25    De mesange    tit (?)
26    D'hypolais    tree warbler
27    De jaseur    waxwing
28    De loriot    oriole
29    De jacana    jacana
30    De grouse (?)    grouse (?!)
31    De lagopede    lagopus
32    De faisan    pheasant
33    De perdrix    partridge
34    De caille    quail
35    D'avocette    avocet
36    De chevalier arlequin    spotted redshank
37    De pluvier guignard    dotterel
38    De pluvier de Virginie (??)    plover (??)
39    De vanneau    lapwing
40    De chevalier cul-blanc    green sandpiper
41    De sterne hybride (??)    tern (??)
42    D'hirondelle de mer    common tern
43    De sterne de Ruppell (??)    tern (??)
44    De goeland    seagull
45    De plongeon    loon
46    De guillemot    guillemot
47    De grand pingouin    great auk
48 & 49    De macareux    puffin
50    De grebe    grebe


Avian Reproduction reference

Why We Fly in V Formation

Why do swans, geese, and ducks fly in V formation?

Because it makes their journey easier.

Everything that flies experiences turbulence that slows it down.  Some of the turbulence is created by the act of flying.  For instance, during lift cones of swirling air called vortices roll off the wingtips and induce drag.

Here's a dramatic NASA photo of a wingtip vortex, enhanced by red smoke.


The right and left wing vortices swirl in opposite directions -- the left spins clockwise, the right counter-clockwise -- resulting in two trailing swirls behind the airplane or bird.  Click here and here for videos.

The induced drag is especially hard on large or heavy birds (swans and geese) and birds with small wings relative to their size (ducks) so these birds line up in Vs to reduce the turbulence.

Here's how it works.

In the photo below, four tundra swans are flying in the direction of the blue arrow.  Behind the leader, the blue lines show that each bird has its right wingtip in line with the left wingtip of the bird ahead of it.


Now I'll draw the vortices and their spinning directions using blue for the left wing, red for the right wing.  Blue/left spins clockwise.  Red/right spins counter-clockwise.

When the blue vortex meets the red vortex at the wingtip, they cancel each other out.   By lining up in this fashion, each bird has one wing that experiences less turbulence.  That makes it easier to fly.

The lead bird is out there alone, though.  He's the only one who gets no assistance so he tires before the rest of the flock.  The flock solves this by changing leaders when the first one needs to rest.  The lead bird drops back into the V and another bird takes his place.

Long, long ago birds solved the problem of wingtip turbulence.  When we invented airplanes we found out what it was all about.


Photo of tundra swans in blue sky by Chuck Tague.  Line of tundra swans by Marcy Cunkelman.  Red vortex photo by NASA via Wikimedia Commons; click on the image to see the original.
Today's Tenth Page is inspired by a diagram on page 123 of Ornithology by Frank B. Gill.

Lumping And Splitting

In last week's Tenth Page I mentioned that DNA test results can lead to lumping, splitting and reordering of bird species in our field guides and checklists.  Sometimes this drives me nuts.

An easy example of lumping occurred in December 2005 when the ABA lumped the black wagtail (Motacilla lugens) with the white wagtail (Motacilla alba).  The black one became Motacilla alba lugens.  They're all the same species, just different races.

Splitting occurs more often as DNA analysis shows that birds we thought were a single species are actually two or more.  Some birders welcome the splits because they get new birds to chase for their Life Lists.  For me, it's confusing ... or exasperating.

Case in point:  Prior to DNA analysis the winter wren (Troglodytes troglodytes) was listed as a single species in Europe, Asia and the Americas.  In November 2010 the ABA officially split it into three (or more) species:

  1. Eurasian wren, Troglodytes troglodytes, in Eurasia. (new common name)
  2. Winter wren, Troglodytes hiemalis, in eastern North America. (new scientific name)
  3. Pacific wren, Troglodytes pacificus, in western North America. (new names all around)

Why does this drive me nuts?

Practically speaking you can only tell these wrens apart by range but in northeastern British Columbia "Winter" and "Pacific" overlap.  Can you tell them apart in the field?  Only by a slight difference in their call notes.  Can you tell them apart in a photograph?  No.  How to be sure which one you've found?  Test his DNA.

The changes are a bookkeeping nightmare.  The Internet is sprinkled with old and new names.  Some birds have changed twice: Baltimore oriole became "northern oriole" (lumped with Bullock's oriole) and went back to Baltimore oriole (re-split).

I can't keep up!  Arg!


(Photo of a winter wren by Steve Gosser taken in October 2010, only a month before the bird's scientific name was changed.
Inspiration for this Tenth Page is from page 70-73 of Ornithology by Frank B. Gill.)

Unlikely Relatives

If you were looking for the flamingo's closest living relative it's unlikely that you'd ever pick a grebe, but it's true.

As DNA testing became perfected in the late 20th century, scientists naturally turned their attention to birds.  What does bird DNA show about their relationships?  The studies told us more than we bargained for.

Pictured above are a pied-billed grebe (Podilymbus podiceps) and an American flamingo (Phoenicopterus ruber).   Based on DNA research (van Tuinen, et al, 2001) the families of grebes (Podicipediformes) and flamingoes (Phoenicopteriformes) are each other's closest living relatives.  Studies indicate they have a common ancient ancestor which is now extinct.

This finding was only the tip of the iceberg.  In many cases DNA testing confirmed previous taxa but in some cases unrelated birds were shown to be related, previously related birds were pulled asunder, taxonomic order had to be revised and scientific names were changed.

This makes for an ever-changing array of new field guides with new names and new orders.  The black-bellied whistling duck is now the first bird on the ABA Checklist.  Years ago the common loon came first.

I love all this new information but renaming the warblers was more than I could bear.  I wish they'd tossed out Setophaga and named them all Dendroica.

(Inspiration for this Tenth Page is from page 70-73 of Ornithology by Frank B. Gill.    Pied-billed grebe photo by Chuck TagueFlamingo photo by Aaron Logan on Wikimedia Commons)