Birds in superstition and folklore

One is lucky, two is lucky, three is health, four is wealth, five sickness, and six death.
- The Children's Mother Goose

The ways in which we watch and learn about birds - HD cameras, high-powered spotting scopes and lenses, and DNA analyzers - are new, but our interest in them is very old. Folklore and legends about birds exist in almost every human culture. Birds and bird-like creatures have been regarded as gods (Egypt's Horus and many Native American tribes), symbols of authority (Zeus's eagle), supernaturally wise (Athena's owl and crows and ravens in general), and harbingers of death and the dead. They are found in many sacred texts, including the Bible, the Torah, the Qur'an, the Bhagavad-gita, and countless oral traditions. To watchers who didn't have the benefit of global knowledge or a scientific framework, the fascinating and sometimes eerie lives of birds could be explained only through supernatural events or powers. Our respect and love for birds has traditionally been tempered with apprehension, since the knowledge they possess could be turned against us.

We hope you enjoy this quick round-up of bird folklore. Happy Halloween!

Birds as associates and companions of deities
Rachel Warren Chad, a co-author of Birds: Myth, lore & legend, states that Deities from cultures around the world have birds associated with them. Doves (bird of Astarte, Aphrodite/Venus, Holy Spirit), ravens (Odin’s familiars in Norse mythology), cranes (sacred bird of Hermes/Mercury, Celtic bird of the moon) and eagles (familiars of Zeus/Jupiter) are among the many species assigned such roles in myth and legend.  They fly between heaven and earth, deliver messages to and from the gods, and signify divine might.

Birds are also found in Christian folklore. In Europe, birds with bright red or pink splotches (robins, crossbills, finches) were said to have been stained with Christ's blood as they attempted to pull thorns from his body or nails from his hands and feet. Another superstition states that the robin got its red breast after taking water to thirsty sinners in Hell. The sparrow gets a bad rap, since it attended the Crucifixion to encourage the guards to torture Jesus, but it's still a very bad idea to kill a sparrow or put one in a cage. Eagles are said to go into seclusion, pluck out all of their feathers, and shed their beak and talons to live longer. While not specifically Christian, this myth (it isn't true) is usually accompanied with Christian symbolism. Eagles are also considered to be one of the four dimensions of creation and a messenger of God.

Birds as harbingers of death
It is hard to believe that a bird could be considered a harbinger of death. But in a great deal of traditional lore, birds fly between earth and heaven or earth and the realms of the dead. As a consequence, some birds became associated with death and the dead, especially dark birds, nocturnal birds, and birds with an eerie or mournful cry. Depending on where you are from, your relatives may have known that:

• If a bird flies into your house, there will soon be a death in the family. One of the surer omens of death is a bird entering the bedroom of a sick person and landing on the bedpost. This belief is so widespread that Snopes has a refutation: https://www.snopes.com/oldwives/bird.asp.
• A white bird or a crow flying against a window at night foretells of a death in the house within a year. A pigeon flying against the window is a sign of death.
• Seeing six crows is a sign of coming death, as is a whippoorwill singing near the house.
• Seeing two turtle doves together in a tree means death is coming. If a sparrow attacks a swallow and throws it from its nest (on or near a home), a son will be born and a daughter will die.
• A woodpecker knocking on the house is a death omen.
• A peacock feather brought into the house is taunting death.
• If you walk under a tree in the evening and an owl hoots right above your head, it means a relative or friend of yours will die within a year.
• If an owl hoots while perched on your rooftop, death will pay a visit. Other parts of the world say that an owl simply hooting in the neighborhood is foreshadowing death nearby.
• To hear a rooster crow at your door is a sign of death.

Birds as omens and talismans

In addition to death, birds might indicate future events or serve as intermediaries between the natural and supernatural world. Crows and ravens in particular have a large body of lore associated with them. Some cultures see them as essentially beneficial, although full of mischief, while others mistrust and fear them.

• In Christian tradition ravens were believed to have special taste for criminals, and to enjoy plucking out the eyes of sinners, although they also fed sacred hermits and were used by Jesus as an example of God's provenance. In the Qur'an, a raven is mentioned as the creature who taught Cain how to bury his murdered brother. In the Talmud, the raven is described as having been only one of three beings on Noah's Ark that copulated during the flood and so was punished. North American and Canadian mythology depicts the raven as a Creator, a rascal, or a trickster. Raven created the world and saved all of the animals from a big flood, but he also created a great deal of trouble among humans for his own amusement...and we have Raven to thank for mosquitoes.
• In Southeast Asia, a crow flying low across one's path as one starts on an important errand or trip is considered an omen, interpreted as favorable or not depending on the direction it crosses.
• Ancient Greeks believed that if a single crow appeared at a wedding breakfast, there would be a divorce. 
• In Sweden, ravens were known as the ghosts of murdered people.
• A destroyed crow’s nest indicates a fire in the area within three days. 
• If a crow lands on a house and caws sorrowfully, a calamity is sure to befall it. If, on the other hand, his joyful “carrow” is heard, it is a sign of good luck. 

Ravens and crows are not the only birds associated with luck.

• It is unlucky to kill a robin or a swallow. Swallows have been considered sacred because they were thought to have flown around the cross of Calvary. In some places, the ill luck from an accidental killing of a robin or swallow can be canceled if burial is given to the creature. The poem 'The Funeral of Cock-Robin' refers to this tradition in a funny way. If you break a robin's egg, something precious to you will soon be broken.
• In England, the stonechat is believed to be continually chatting with the Devil. In parts of the British Isles the chicken is also thought of as a bird of ill omen, due to an old idea that he “crowed for joy” at the hour of crucifixion. Magpies carry a drop of the Devil's blood under their tongues and a lone magpie loitering near your house means that the Devil is afoot and stirring up trouble!
• In Norway, those in search of a drowned body would row around the body of water with a rooster aboard, believing that the bird would crow when the boat reached the spot where the corpse was. 
• In Ireland, sparrows, stares and plovers are thought to be on friendly terms with the fairies. The lark and swallow are both birds of good omen, as long as the swallow does not rest on the housetop. 
• In France, there was once a belief that quail could foretell the price of wheat with the number of their calls, prompting it to be called the “Bird of Prophecy”. The ancient Romans practiced ornithomancy, a form of divination that took omens from the flights and cries of birds. If a bird cries from the north, ill luck will ensue; if from the south, a good harvest; if from the west, good luck; and if from the east, love.
• An American superstition holds that to possess the feathers of a peacock in your home is unlucky. It is also unlucky to have peacock feathers on the stage or comprising any part of a costume, prop, or scenery!
• In Poland, it was believed that girls who died unmarried turned into doves, while those who died married turned into owls. It was also believed that owls did not come out during the day because they were so beautiful and would be mobbed by other birds out of jealousy.
• Did a bird poop on you today? Too bad if it didn't, since Russians know that bird poop brings good luck! But it is bad luck to see an owl during the day (videos of owls don't count as far as we know).
• If the first bird you see on Valentine’s Day is a goldfinch, it means your spouse will be rich.
• Many birds are believed to carry dead souls or messages from the dead, including sparrows, blackbirds, ravens, swifts, and even doves. In France, the souls of unbaptized children who die are said to become birds until they gain entry to heaven. 

Do you feed or water birds? If not, the dead might be hearing about your bad behavior! In parts of Turkey, small vessels of water are sometimes placed upon graves for the birds to drink. Some marble tombs have basins for water as well, as birds are thought to carry messages about the living to the dead. The water is left to curry favor with the birds, which prevents them from carrying unfavorable messages to dead loved ones.  So get out there and fill those feeders before it's too late!

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Things that helped me learn and write about this subject:

• https://voices.nationalgeographic.org/2016/11/08/delving-into-cultural-myths-tales-and-beliefs-about-wild-birds/. This book looks fantastic!
• http://www.perspectivesmagazine.sk/news/ravens-and-crows-in-mythology-folklore-and-religion/
• https://en.wikipedia.org/wiki/Cultural_depictions_of_ravens
• https://archive.org/stream/birdsinlegendfab00inge/birdsinlegendfab00inge_djvu.txt
• http://www.pararesearchers.org/index.php?/20080801457/Folklore-Mythology/Death-Omens.html
• http://superstitiondictionary.com/omens-of-death-folklore-and-superstition/
• http://superstitiondictionary.com/superstitions-about-birds/

Hunting Lead-Free

With firearm deer hunting season getting ready to start in many places in the midwest, it seemed like a good time to remind people to hunt lead-free. Our director John Howe does so, and so do many of my friends, most of whom are concerned about lead's impact on wildlife and on themselves. Ingesting lead ammunition kills Bald Eagles and other birds of prey: ingesting lead fishing tackle kills loons and other waterbirds. Lead poisoning has been documented in 63 species of birds since 1939, including eagles, ravens, pheasants and other game birds, owls, rails, gulls, buzzards, kites, vultures, condors, falcons, red-tailed hawks, white-throated sparrows, yellow-rumped warblers, and solitary vireos. If you hunt, do wildlife and your family a favor and switch to non-toxic ammo.


This video about the issue features Kay Neumann from SOAR

I've compiled some information about wildlife exposure to lead. If you are looking for places to purchase non-toxic ammo, follow this link to our website: https://www.raptorresource.org/learning-tools/hunt-and-fish-lead-free/ or check out SOAR's excellent resources: http://soarraptors.org/hunt-and-fish-lead-free/. If you aren't familiar with non-toxic shooting, check out this Tom Roster's 2016 non-toxic shot lethality table: https://gf.nd.gov/gnf/hunting/docs/tom-roster-nontoxic-shot-lethality-table.pdf.

Is lead really a problem? 

Absolutely. Lead is a toxic metal with no known safe exposure levels for humans or wildlife. In the United States, an estimated 3,000 tons of lead are shot into the environment by hunting every year, another 80,000 tons are released at shooting ranges, and 4,000 tons are lost in ponds and streams as fishing lures and sinkers. As many as 20 million birds and other animals die each year from subsequent lead poisoning (yes, this shocked me, but I verified it with the source (http://bit.ly/2d7h7KJ and http://bit.ly/2e0eYXs).

Lead is a big killer of Bald eagles. From 1975 to 2013, the National Wildlife Health Center conducted a mortality study on the carcasses of 2, 980 Bald Eagles and 1,427 Golden Eagles. Their summary looked like this:

Cause of death	Bald eagle	Golden eagle	Total
Drowned	11 (0.4%)	3 (0.2%)	14 (0.3%)
Electrocution	372 (12.5%)	381 (26.7%)	753 (17.1%)
Emaciation	176 (5.9%)	90 (6.3%)	266 (6.0%)
Disease	155 (5.2%)	39 (2.7%)	194 (4.4%)
Poisoned	762 (25.6%)	117 (8.2%)	879 (19.9%)
Shot	303 (10.2%)	196 (13.7%)	499 (11.3%)
Trapped	59 (2.0%)	39 (2.7%)	98 (2.2%)
Trauma	681 (22.9%)	84 (26.9%)	1,065 (24.2%)
Undetermined	298 (10.0%)	131 (9.2%)	429 (9.7%)
Total	2,980	1,427	4,407

The study found that 63% of the poisoned bald eagles and 58% of the poisoned golden eagles had been killed by lead, which was the second-biggest killer of bald eagles. Note that the study did not look at whether lead was a factor in trauma deaths (the biggest killer of eagles if poisoning is broken into lead poisoning and everything else). However, other studies have found that sub-lethal amounts of lead play a large role in eagle collisions. Lead is an even bigger killer of eagles than this study indicates.

How are birds and other animals exposed to lead?

They eat it. Fish-eating birds like bald eagles and loons eat fish that have ingested lead sinkers or other tackle, while scavenging birds like bald eagles, vultures, condors, and some hawks feed on gutpiles left by hunters that contain fragments of lead ammo. They also eat the carcasses of animals that weren't recovered and eventually died of their wounds. Waterbirds like trumpeter swans, mallard ducks, and loons ingest ammunition or lead sinkers while foraging in lakes, and upland birds like pheasants mistake shot for seeds or grit and eat it.

If I switch to non-toxic ammo, will it really make a difference? 
Absolutely! Switching to non-toxic ammo will prevent lead from entering the environment, which will keep it out of the bodies of birds, animals, and people that enjoy eating wild game. Here's an example: In 1991, the U.S. Fish and Wildlife Service outlawed the use of lead ammunition to hunt migratory waterfowl after it was estimated that 2 million ducks died annually from ingesting lead pellets. A follow-up survey of ducks on the Mississippi Flyway found that the ban on lead shot reduced lead poisoning deaths of Mississippi Flyway mallards by 64 percent, while overall ingestion of toxic pellets declined by 78 percent over previous levels. By significantly reducing lead shot ingestion in waterfowl, the ban prevented the lead poisoning deaths of approximately 1.4 million ducks in the 1997 fall flight of 90 million ducks. Plenty of ducks were still harvested, but far fewer died accidentally after ingesting lead.

Does non-toxic ammo and fishing tackle actually work? 

No one wants to switch to ammo or tackle that doesn't work, but non-toxics work very well! Let's start with wildfowl. The total number of migratory waterfowl harvested nationwide declined steeply beginning in about 1984, but started rising again after the ban on lead ammo was enacted, as shown by the chart. Requiring the use of non-toxic shot did not negatively impact waterfowl hunting, but did prevent ducks, geese, and many other animals from coming into contact with lead shot by ingesting it directly or feeding on lead-poisoned animals or carcasses containing shot. How about doves? A multi-year study by the Texas Parks and Wildlife Department found no statistical difference between lead and steel ammunition in terms of doves hit, missed, crippled, and killed at all ranges. How about other game, including deer? A large study done in Germany found that lead-free rifle bullets were as effective at killing wildlife as conventional lead bullets. How about deer and only deer? This article in Whitetails, the magazine of the Minnesota Deer Hunters Association, discusses non-toxic ammo with eight hunters that made the switch.

Saving Our Avian Resources has done a lot of advocacy for non-toxic shot and they have wonderful information on their website. A few figures that struck me:

• A study of causes of mortality in eagles submitted to the National Wildlife Health Center between 1975 and 2013 found that trauma and poisonings (including lead poisoning) were the leading causes of death for bald eagles throughout the study period.
• 56% of all eagles admitted to Iowa rehabilitators between 2004 and 2008 had abnormal lead levels in their blood. This ranged from a low of 37.5% in 2004 (with 62.5% of eagles being tested) to a high of 70.0% in 2005 (with 90.0% being tested).
• The University of Minnesota’s Raptor Center in St. Paul received 117 lead-poisoned bald eagles during the winter of 2009. In 2012, Dr. Pat Redig co-authored this paper about spent ammunition and lead poisoning in bald eagles.
• In Canada and the USA, approximately 10–15% of recorded post-fledging mortality in Bald and Golden Eagles was attributed to the ingestion of lead shot from prey animals (Scheuhammer and Norris 1996). Elliott et al. (1992) found that 14% of 294 sick, injured. or dead Bald Eagles in British Columbia (1988 to 1991) were lead-poisoned and an additional 23% sub-clinically exposed.
• A 2012 study by a team at the University of California at Santa Cruz found that 30 percent of blood samples taken from condors each year showed levels of lead high enough to cause significant health problems and that 20 percent of the free-flying birds required treatment to remove lead. From 1992 to 2012, the cause of death was established for 123 condors in California, Arizona and Baja California, Mexico; lead was responsible for 42 of the mortalities (https://goo.gl/fmK8Ku). While lead poisoning can kill directly, lead toxicity is also a factor in collision deaths and injuries. According to the Raptor Center, about 85% of eagles that come in with collision injuries also have elevated lead levels. 

The best time to switch to lead is now! Good luck with your lead-free hunts this year!

References

• Causes of Mortality in Eagles Submitted to The National Wildlife Health Center 1975–2013: http://www.jstor.org/stable/wildsocibull2011.38.4.697
• Bald Eagle Lead Poisoning in Winter: http://www.peregrinefund.org/subsites/conference-lead/PDF/0119%20Neumann.pdf
• Lead from spent ammunition: a source of exposure and poisoning in bald eagles: http://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=1164&context=hwi
• A Global Update of Lead Poisoning in Terrestrial Birds from Ammunition Sources Harvest Trends: http://flyways.us/regulations-and-harvest/harvest-trends
• FWS Survey on waterfowl and lead: http://www.fws.gov/pacific/news/2000/2000-177.htm
• Minnesota Eagles Fall Prey to Lead: http://www.startribune.com/local/137358413.html
• SOAR: Hunt and fish lead-free
• SOAR: Lead in the environment
• Humane Society of America: Lead Ammunition

What's on the menu at Fort St. Vrain? An exploration of nest remains, part II

The last time we blogged about prey remains from Xcel Energy's Fort St. Vrain bald eagle nest, we talked about mammals. This time, we're going to explore fish and turtles! In all, we found 35 fish remains, seven prairie dog skulls and one foot, one desert cottontail skull, one common muskrat skull, three western painted turtle shells, and some unknown vertebrae. Even in a relatively dry environment, the eagles show a clear preference for fish. Our aquatic remains included:

• seventeen opercular bones (eleven left and six right, from at least twelve different fish)
• eight preopercular bones 
• one otolith 
• four skull tops 
• five skull fragments, and; 
• three turtle shells. 

So what are opercular bones and otoliths? The operculum, which includes the preopercular and opercular bones, is a series of bones found in bony fish that serves as a facial support structure and a protective covering for the gills; it is also used for respiration and feeding.

The opercular series. Nine/yellow is the opercular bone. Six/red is the pre-opercular bone

Otoliths are a calcium carbonate structure in the inner ear of vertebrates. They act as gravity, balance, movement, and directional indicators in all vertebrates, and have a secondary function in sound detection in higher aquatic and terrestrial vertebrates, including fish. Vertebrates have three pairs: the astericus (Ast), lapillus (Lap), and sagitta (Sag). Many fish can be identified to genus and species by their sagittal otoliths but alas, we found only one!

At least we had several opercular bones. While we couldn't use them to determine genus and species, they could determine the size of the fish the eagles were bringing in. Several papers document a close relationship between the size of the opercular bone and the total length (from nose to tail) of the fish. I chose Hostetter and Munroe's 1993 paper Age, growth, and reproduction of Tautoga omtis, which used the formula log10 TL = 1.2916+0.860 log10 OR for males. The paper meticulously documented Hostetter and Munroe's methodology and results, which were used in subsequent studies of several fish species. It was also well-cited and required nothing more than a dial calipers, intact opercular bones, and a good calculator - three things I had on hand!

I used the dial calipers to determine Opercular radius (OR). which Hostetter and Monroe define as the distance from the articular apex center to the midpoint of the posterior margin of the opercle. It looked something like this...

Opercular and preopercular bones of our largest fish. 

I ran my measurements through the formula log10 TL = 1.2916+0.860 log10 OR to obtain the lengths below (more on that at the end of the blog). While we collected 17 bones, only 14 were intact enough to use.

OR	Total length	Number/side
61mm	26.3" / 668.02 mm	1 / left
47mm	20.9" / 530.86 mm	1 / left
46mm	20.6" / 523.24 mm	1 / right
43mm	19.4" / 492.76 mm	2 / both left
42mm	19.0" / 482.60 mm	2 / both right
41mm	18.6" / 472.44 mm	2 / left, right
40mm	18.3" / 464.82 mm	3 / left, right, left
34mm	15.9" / 403.86 mm	2 / both left

While I was impressed by the largest fish, it was a real outlier. The average fish size was 19.0" - a nice size at just a little over 1-1/2 feet long. So what kind of fish would they be likely to be and how heavy might they have been? I checked out a fishing report for the St. Vrain state park and emailed the Laughing Grizzly fly shop to find out! Given the size of the fish and the stretch of the river, Mike suggested either sucker or bass, with the outlier possibly belonging to a carp. Their length/weight profiles look something like this:

• Common Carp: 16 to 26.5 inches at 2 pounds to 10 pounds
• Largemouth Bass: 16 to 25 inches at 2.4 pounds to 9.10 pounds
• White Sucker: 16 to 20 inches at roughly 4 to 6 pounds 
• Longnose Sucker: 15-25 inches at 1 to 2 pounds (although Montana's field guide states that the largest can be around 5 pounds and fish of up to 7.3 pounds have been reported)

In addition to sizing fish, opercular bones can also be used to age fish. Like trees, they produce annular rings that can be counted once the bones have been cleaned and held up to a strong light. However, I was confused by the age of my fish. Almost every opercular I counted yielded an age of four or older, with several between six and nine years of age and the oldest (the outlier) about fourteen. I hadn't expected my fish to be as old or as big as they were. Was I counting wrong? What was going on?

Operculars. Mr. Big is at left. It was the oldest and the largest opercular bone.

As eagle cam watchers might recall, sucker fish rise in the spring and early summer to spawn on gravel beds and sand bars. Every year, Dad Decorah and Mr. North haul in suckers by the dozens once the run starts, sometimes bringing in more than one at a time! However, Longnose Sucker don't become sexually mature until they are between five and nine years of age, while White Sucker don't reach sexual maturity until they are three to eight years old. This means that spawning suckers are a minimum of three years old at spawning, and could easily be older. Finally, my large old bones make sense! Do we know that these fish are suckers? No - but age and size as determined by the opercular bones fit the species, especially given the presence of suckers as identified by local fishing guides, their age at sexual maturity, the amount of sand and gravel bars in the area, and the seeming preference of eagles for suckers when given the choice between suckers and, say, trout. Bob would love this, since he theorized back in 2012 that sucker fish spawning could be the Midwest's equivalent of a salmon run when it comes to protein sources for eagles and other animals that eat them. We'll be watching closely during the spawning season in 2018 to see if we can identify the fish that Ma and Pa FSV bring in! (Amy's note: There were two very distinct shapes of opercular bone, which makes me think that at least two different species were brought into the nest. One was rounded [Mr. Big and several of the others], while the other was more angular).  

Of course, fish weren't the only aquatic animal the eagles brought into the nest. We also found three turtle shells. Alan Resetar, the McCarter Collections Manager for the Chicago Field Museum's Amphibian and Reptile Collection, identified them as spiny softshells (Apalone spinifera). This was very helpful, since I originally thought they might be western painted turtles or small snapping turtles. He also provided a link to this guide for identifying turtle shells and remains: http://fieldmuseumlibrary.worldcat.org/title/turtle-atlas-to-facilitate-archaeological-identifications/oclc/35793760. Take a look at the picture below, which clearly illustrates how the spine and ribs are fused to the shell, giving turtles their distinctive walk.

The underside of a turtle's shell 

So what did we learn? Collecting prey remains from the Fort St. Vrain nest gave us a couple of unexpected insights. As dry as the area is, aquatic animals (especially fish) are still an important part of Ma and Pa FSV's diet - something we didn't expect. The spiny softshells were a surprise, since they are at the extreme western end of their range. And like the Decorah and Decorah North eagles, the Fort St. Vrain eagles appear to take advantage of the spring sucker run, which comes at a very timely point in the lives of their young! While some specific prey details are different (prairie dogs!), the remains we found fit within the larger framework of bald eagle behavior - getting the most food for the least amount of effort and risk expanded. Benjamin Franklin famously called bald eagle behavior lazy, but it takes experience and intelligence to know where and how to find food, especially in a beautiful but unforgiving place like Colorado's Front Range.

Xcel Energy, thanks for all of your hard work and support. You are wonderful eagle and falcon friends, and I look forward to collecting prey remains from Fort St. Vrain next year! I was quite fascinated by this nest, which is much drier and 'stickier' than our Iowa nests. The lack of humidity means that materials don't tend to compost in the nest, although the eagles still prepare the area under the nest cup and strip bark from the sticks they bring in. We have three eagle nests to watch in Iowa and Colorado. What can we learn from their differences and similarities? We look forward to finding out!

Did you know?

I wish we found more otoliths, since researchers are using them to model climate impacts: https://blog.csiro.au/fish-ear-bones-point-to-climate-impacts/. I am hoping to send our fish and mammal collection to the Field Museum in Chicago!

Most of the fish we found were within the carrying capacity of Ma and Pa FSV. Under standard conditions, Bald Eagles can lift and carry around 60% of their body weight, and in some circumstances they can carry more! A link: https://raptorresource.blogspot.com/2015/11/how-much-can-bald-eagle-carry.html

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Things that helped me learn and write about this topic:

• Alan Resetar, McCarter Collections Manager, Amphibian and Reptile Collection, Field Museum
• Age, growth, and reproduction of tautog Tautoga onitis: http://fishbull.noaa.gov/911/hostetter.pdf
• A Guide to aging Yellow Pike and Walleye (if you are a fishing family, this provides a guide for kids): http://www.rebeccaeberts.ca/wp-
• content/uploads/2015/01/EbertsAgingArticle_pg39_outdooredge22.pdf
• Vestibular system. Your ears might be stranger than you think! https://en.wikipedia.org/wiki/Vestibular_system
• Laughing Grizzly Fly Shop. Hit them up for fishing if you are in Longmont, Colorado - these guys know their business!
• Luke Ries. Thanks for the help on the math formula!
• Turtles of Colorado:
  http://cpw.state.co.us/Documents/Education/StudentActivities/COHerpQuickKey.pdf

Birds on Radar, October 3rd, 2017

At whatever moment you read these words, day or night, there are birds aloft in the skies of the Western Hemisphere, migrating. If it is spring or fall, the great pivot points of the year, then the continents are swarming with billions of traveling birds...
- Living on the Wind: Across the Hemisphere with Migratory Birds

After three nights and days of rain, storms, and winds from the south, last night was finally clear and calm. The full moon was so bright that no light was required as I walked up and down my driveway and around our yard. While I couldn't see any birds, a few short flight calls overhead told me that a great river of birds was flowing in the sky above me.

Bald eagles and other bird of prey migrate during the day, when they can take advantage of thermal soaring to help lift and carry their large bodies long distances. But many songbirds migrate in large flocks or swarms at night. Avian predators are less active, skies are often less turbulent, the cooler night air is slightly denser and helps birds dump heat and like sailors, birds can use the stars for navigation across an otherwise relatively featureless landscape.

How many birds were migrating last night? Two words: Green Doughnuts.



The map above shows reflectivity, defined as the amount of transmitted power returned to the radar receiver after hitting precipitation, compared to a reference power density at a distance of 1 meter from the radar antenna. In short, when radar hits stuff, it gets bounced back. The more radar that gets bounced back relative to the reference, the more intense or denser the stuff it is hitting: precipitation, flocks of birds, migrating bats, insects rising into the sky, and so on.

If you look at the map above, you can see a line of storms moving to the east. Some of these storms are dropping quite a bit of precipitation, as shown by the yellow and red colors in Michigan's Upper Peninsula. But you can also see blue and green doughnuts or blooms blowing up around sunset (which occurred at 6:47pm CT in eastern Minnesota and Iowa last night). The unique pattern, lower reflectivity, behavior (an ebb and flow that begins at sunset and begins to peter out at about 1:30am), weather, and time of year all tell us that these are migratory birds.

So why was I excited about green doughnuts? Check out the reflectivity key below...

The colors represent the strength of returned energy to the radar expressed in values of decibels (dBZ). As we stated earlier, the amount of radar reflected back to the ground unit is proportional to the number and diameter of stuff - drops/flakes/birds/insects - per unit volume. The US Weather service defines rainfall rates and types here, while the Cornell Lab of Ornithology defines bird 'rates' (but not types) as follows:

• Minimal migration: < 5 dBZ — fewer than 59 birds per cubic kilometer
• Light migration: 5-10 dBZ — approximating 59-71 birds per cubic kilometer
• Moderate migration: 10-20 dBZ — approximating 71-227 birds per cubic kilometer
• Heavy migration: 20-30 dBZ — approximating 227-1788 birds per cubic kilometer
• Extreme: >30 dBZ — more than 1788 birds per cubic kilometer (actually  occurs at some times in very rare circumstances)

Blue doughnuts are pretty typical, at least during the summer months. But green doughnuts are something else! Last night's radar shows heavy migration that approached extreme migration in some places. As I walked and listened, I thought it was probably a pretty special night. I can't believe how special it really was! I'll be out looking and listening for birds again tonight.

Additional Resources
How do normally diurnal birds become temporarily nocturnal? Read more about that here (warning - this is a dense read): https://www.nature.com/articles/srep34207

The Cornell Lab of Ornithology publishes bird forecasts and migration reports on their website at http://birdcast.info/. Check it out and keep those feeders filled for hungry seed, nut, and suet eaters that are resting and refueling in your yard!

BirdNote did an excellent story about nocturnal migration. You can listen to that here: https://www.birdnote.org/show/nocturnal-migration-songbirds.

The Old Bird studies nocturnal flight call activity. While he isn't the only one, almost everyone involved in this activity cited him as the original. Check out his website at: http://oldbird.org/.

Thanks to the University of Wisconsin, we have a national radar map here: http://www.raptorresource.org/maps/UW_Composite_Radar/ and one showing migration for the great lakes/upper midwest here: http://www.raptorresource.org/maps/UW_Composite_Radar/. These maps archive data over several months. We encourage you to check them out and compare nights - summer versus winter, stormy nights versus calm nights, and good flight nights.

Good luck birds, and we'll see you next spring!