Category Archives: Musings & News

Not Truly Blue

Purple honeycreeper, Trinidad (photo by Greg Smith via Flickr, Creative Commons license)
Purple honeycreeper, Trinidad (photo by Greg Smith via Flickr, Creative Commons license)

15 September 2021

If you take photos of purple things you may have noticed that your camera renders the images as blue.

My classic example is the purple honeycreeper photo which I used on the blog in 2014. The bird looks blue in the photo above but in the photo below, taken with a different camera or edited differently, the bird is purple. The field guide says he is deep violet-blue, thus named the purple honeycreeper.

Purple honeycreeper as he looks in real life (photo from Wikimedia Commons)

The purple-turns-blue problem is caused by the fundamental difference between how our eyes see violet light and how a camera does.

Our eyes have color receptors that pull in three colors of light — short wavelength (S) blue, middle wavelength (M) green, and long wavelength (L) red — with sensitivity peaking at certain wavelengths. Our brains process color by noting the ratios from each receptor. When we see purple our brains detect information from the blue and red sensors.

Camera color receptors pull in the same colors too but they peak at slightly different wavelengths than our eyes and the camera processes blended colors differently than our brains do. Robert Schleif at Johns Hopkins University explains:

Digital cameras distinguish colors in about the same way as the human eye. Most likely however, distinguishing colors at the blue [violet] end of the spectrum utilizes the blue and green sensors rather than the blue and red sensors used in humans.

Sensing Violet: The Human Eye and Digital Cameras Robert Schleif, Johns Hopkins University

His diagram, link-embedded below, shows the difference between human and Nikon D70 camera color sensitivity.

image embedded from Sensing Violet: The Human Eye and Digital Cameras, Johns Hopkins Dept of Biology, Robert Schleif

Humans register purple in our brains by seeing blue+red. Most cameras register purple using blue+green so they cannot match the color we see.

For example, here’s an unedited photo of a purple aster taken by my Pixel 5 cellphone camera. The camera makes it blue.

The Pixel photo editor can fix it. I used the “Enhance” filter to come closest to the original flower color but this makes the photo too bright to my liking.

Adjusted by Pixel cellphone “Enhance” edit (photo by Kate St. John)

My laptop photo editor can fix it, too, by simply pumping up the red. It’s close to the right color but still not perfect.

Aster photo, adjusted by hand to pump up the red (photo by Kate St. John)

So now you know why deep violet looks blue in many photos. Purple honeycreepers and purple asters are not truly blue.

For more information see Robert Schleif’s article: Sensing Violet: The Human Eye and Digital Cameras.

p.s. Light is violet. Purple is a color constructed by our brains. Bird brains see the color purple differently than we do because they can see ultraviolet light. I’m sure the purple honeycreeper looks quite different to his fellow birds. Perhaps he is ultraviolet.

(photos from Wikimedia Commons and Kate St. John, graph is link-embedded from Sensing Violet: The Human Eye and Digital Cameras, Robert Schleif, Johns Hopkins University Department of Biology)

Functional Grass?

Aerial view of a golf course in Pennsylvania (photo by formulanone via Flickr Creative Commons license)

26 August 2021

When I wrote on Tuesday about non-functional grass in Las Vegas, several of you remarked on the Valley’s many golf courses that use so much water. Should they be considered non-functional grass?

Since I’m a birder and not a golfer I would view golf courses as “non-functional” except that some are very good for birds. Courses managed for low chemical use, clean water, and interspersed wildlife habitat are great for birds, especially when their location is an oasis in the midst of other land uses. Courses can achieve these goals and be recognized for their efforts through the Audubon Cooperative Sanctuary Program for Golf Courses.

The Bob O’Connor Golf Course in Schenley Park, affectionately known as The Bob, is just such an oasis. Audubon certified since 2012, the course is savanna habitat interspersed with thickets and bordered by forest and residential neighborhoods.

Near Hole 14 at Schenley Park’s Bob O’Connor golf course (photo by Kate St. John)

I see birds at The Bob that are hard to find elsewhere including nesting orchard orioles, barn and tree swallows following the mowers, and merlins in winter.

Read about The Bob’s bird amenities in The Rough is For the Birds. It’s one of only six Audubon certified golf courses in the Pittsburgh area.

  1. The Bob O’Connor Golf Course (also called The Bob), Pittsburgh
  2. Brightview at Youghiogeny Country Club, McKeesport
  3. Butler’s Golf Course, Elizabeth
  4. Cranberry Highlands Golf Course, Cranberry Twp, Butler County
  5. Diamond Run Golf Club, Sewickley
  6. Treesdale Golf and Country Club, Gibsonia

Birds will tell you these golf courses are functional.

(photos by formulanone via Flickr Creative Commons license and Kate St. John)

Panther Hollow Lake is Doing Its Job

Panther Hollow Lake is full, 13 August 2021 (photo by Kate St. John)

16 August 2021

When I walked around (pond-sized) Panther Hollow Lake in Schenley Park last Friday, I had to dodge high water. On Saturday I expected to see the same water level, or even higher, but it had dropped significantly. Panther Hollow Lake is doing its job.

Panther Hollow Lake has a smart valve governed by the solar-powered weather instrument in the photo below. The smart valve knows the weather forecast and closes during heavy rain events to hold back fresh water that otherwise flows into Pittsburgh’s combined sewer system. After the danger has passed and before the next storm the valve slowly releases water to provide room in the lake for the next downpour. Thus Panther Hollow Lake prevents downstream flooding in The Run neighborhood.

At normal water level three concrete steps edging the pond are exposed. On Friday 13 August all but the top step were hidden (above) and some walkways were flooded (below).

High water. Level is controlled by solar-powered instrument, 13 Aug 2021 (photo by Kate St. John)
High water. A single concrete step at the cattails, 13 August 2021 (photo by Kate St. John)

When I returned 24 hours later the water was lower and all three steps were exposed. Here are the same three scenes on Saturday 14 August.

Panther Hollow Lake is lower, 14 August 2021 (photo by Kate St. John)
Water no longer floods the walkway, 14 August 2021 (photo by Kate St. John)
Three steps at the cattails, 14 August 2021 (photo by Kate St. John)

Today’s forecast calls for thunderstorms with potentially heavy rain. Panther Hollow Lake is ready. The smart valve is doing its job.

p.s. Panther Hollow Lake’s concrete steps will be removed during the Four Mile Run Stormwater Project that will change the lake significantly! Click here to read about the project.

(photos by Kate St. John)

OK to Feed Birds Again; end of mysterious illness restrictions in PA

Northern cardinal at bird feeder (photo from Wikimedia Commons)

14 August 2021

Happy news!

In July the PA Game Commission (PGC) urged Pennsylvanians not to feed birds because of the mysterious illness killing them in 11 states, including PA. Yesterday they announced an end to bird feeding restrictions. It’s OK to feed birds again in Pennsylvania!

Put out your bird feeders! Fill your bird baths!

Robin and cedar waxwings at bird bath (photos from Wikimedia Commons)

They never found out what caused the mysterious illness but it faded away on its own.

Read the PA Game Commission press release here.

(photos from Wikimedia Commons; click on the captions to see the originals)

Birds’ Inner Ears Can Recover Lost Hearing

American robin, watching and listening (photo by Joel Kluger via Flickr Creative Commons license)

12 August 2021

On Monday when I wrote about the handsome trig (red-headed bush cricket) that sings loudly at 7000 Hertz, I mentioned that upper range hearing loss prevents me from hearing him. Hearing aids help a little but nothing can fix it. My hearing will never return to its youthful ability.

Birds don’t have this problem. If the loss is in their inner ear, their bodies repair the damage. Learn more in this vintage article: Birds Can Recover Lost Hearing.

Perhaps birds can recover their hearing because their lives depend on it. Gene Henderson reminded me of a high-pitched danger call that American robins make. At 7200 to 8400 Hertz it’s now outside my hearing range. Can you hear the four calls in the recording below at 2,5,8 and 11 seconds? They look like checkmarks on the sonogram.

American robin danger call (recording by Kate St. John)

(photo by Joel Kluger on Flickr, recording by Kate St. John)

Update Aug 1: Mysterious Bird Illness is Fading Away

American robin fledgling in DC (photo from Wikimedia Commons)

UPDATE 13 Aug 2021: The PA Game Commission has announced an end to bird feeding restrictions. The illness has faded away on its own.

1 August 2021

A few days ago there was hopeful news from Audubon Society of Western PA about the mysterious deaths of songbirds, especially fledglings, in 11 states and DC. The mysterious illness is fading away.

Cornell Wildlife Health Lab at Cornell University has even better news:

As the mysterious illness killing birds lessens, scientists at the Cornell Wildlife Health Lab believe the cause may have been the recent cicada eruption.

Cornell experts not overly alarmed by mysterious songbird sickness, Ithaca Times, 28 July 2021

Cornell’s cicada hypothesis is based on data from the National Wildlife Health Center and the consortium of wildlife agencies investigating the mysterious deaths, summarized here from the Ithaca Times article:

  • The illness appeared about a week after the Brood X cicadas emerged in mid-May.
  • The geographic distribution of the illness matches the Brood X map, including its non-contiguous nature, yellow on the map below.
  • The illness did not spread to nearby states that did not have Brood X cicadas.
  • The illness waned as the cicadas died off and dropped precipitously after the cicadas disappeared.
Active periodical cicada broods in U.S. (2013 map from USGS via Wikimedia Commons)

This is great news for western Pennsylvania. We do not have Brood X cicadas, instead we have Broods V and VIII, the last of which appeared in the Pittsburgh area as Brood VIII in 2019. It will be 12 to 15 years before they re-emerge: Brood V in 2033 and Brood VIII in 2036. If the problem was caused by magicicadas we’re off the hook in Pittsburgh for a very long time.

Brood V Magicicada in Pittsburgh, 30 May 2016 (photo by Kate St. John)

Nature doesn’t follow state lines and political boundaries but state agencies have to. Thus all of Pennsylvania was told to stop feeding birds until scientists learned more about the mysterious bird deaths. Scientists are getting close to an answer and soon (I hope!) we’ll be able to feed birds again.

Read more about the cicada connection at Cornell experts are not overly alarmed by mysterious songbird sickness, Ithaca Times, 28 July 2021.

Learn about the white fungus that infects the cicadas at Cicadas face bizarre “death zombie” fungus that eats away at their butts, CNET, 24 May 2021.

(robin photo and map from Wikimedia Commons; click on the captions to see the originals). Magicicada photo by Kate St. John)

How Shallow Is Lake Erie?

Sunset over Lake Erie at Presque Isle State Park (photo from Wikimedia Commons)

14 July 2021

In summer, folks in western Pennsylvania and northern Ohio flock to Lake Erie‘s shore to beat the heat. The water provides a respite but in July the western end is hotter than anywhere else in the Great Lakes. That’s because Lake Erie is shallow and shallow water is quick to take on the temperature of the surrounding air. So how shallow is Lake Erie?

Lake Erie is the fourth in line of the five Great Lakes and happens to be fourth largest by surface area — 9,940 square miles.

map of the Great Lakes (illustration from Wikimedia Commons)

But as you can see in this bathymetric map it is also the shallowest (blue is deep, red is shallow). Lake Erie’s average depth is only 62 feet with the deepest spot just 210 feet near Long Point, Ontario.

Great Lakes bathymetry map from Wikimedia Commons

It’s easier to see how shallow it is in this diagram from Michigan Sea Grant. Even Lake Ontario, the smallest by surface area, is 3.8 times deeper! (Lakes Michigan and Huron are superimposed on each other because they have the same pool level, 577 feet above sea level. Click here to see the complete diagram.)

Great Lakes System Profile (cropped diagram from Michigan Sea Grant via Flickr Creative Commons license)

Since the shallowest water is first to heat and first to freeze, the surface temperatures roughly match the lake depths. As of yesterday, 13 July 2021, the water at the western end of Lake Erie was close to 80 degrees F.

Great Lakes Surface Environmental Analysis, 12 July 2021 (map from Great Lakes Environmental Research Lab)

Fortunately the temperature has not yet spawned harmful algae blooms (HAB). If you’re going to the western end of Lake Erie this month, check the Lake Erie HAB forecast here before you go.

The lake is warm because it is so shallow. See the current temperature map here.

(photo and first two maps from Wikimedia Commons, Great Lakes system profile from Michigan Sea Grant, Great Lakes Suface Temperature from NOAA; click on the captions to see the originals)

Mysterious Illness is in PA: Stop Feeding Birds

Fledgling European starling afflicted with mysterious disease (photo by National Parks Service photographer Leslie Frattaroli via

2 July 2021

UPDATE 13 Aug 2021: The PA Game Commission has announced an end to bird feeding restrictions. The illness has faded away on its own.

The mysterious songbird illness that is blinding and killing songbirds in six states has now spread to Pennsylvania and Delaware. Yesterday the PA Game Commission advised the public to remove feeders and bird baths to slow the spread.

Symptoms of the illness include a discharge and/or crusting around the eyes, eye lesions, and/or neurologic signs such as falling over or head tremors. Infected birds always die. Scientists are investigating but still don’t know what’s causing it.

The disease has been reported in 27 Pennsylvania counties in these species: blue jays, European starlings, common grackles, American robins, northern cardinals, house finches, house sparrows, eastern bluebirds, red-bellied woodpeckers, Carolina chickadees, and Carolina wrens. Tri-State Bird Rescue and Research in Newark, DE has found that the disease primarily affects fledgling European starlings, blue jays, and common grackles.

Counties in Pennsylvania reporting mysterious bird disease as of 1 July 2021

Yesterday Audubon Society of Western Pennsylvania (ASWP) joined the PA Game Commission in urging the public to follow these precautionary measures:

  • Cease feeding birds and providing water in bird baths until this wildlife mortality event has concluded to prevent potential spread between birds and to other wildlife.
  • Clean feeders and bird baths with a 10% bleach solution.
  • Avoid handling dead or injured wild birds. Wear disposable gloves if it’s necessary to handle a bird.
  • Keep pets away from sick or dead birds as a standard precaution.
  • To dispose of dead birds, place them in a sealable plastic bag and discard with household trash. This will prevent disease transmission to other birds and wildlife.

To underscore the point, Audubon Nature Stores will discontinue the sale of seed and bird feeders for the time being.

Do your part. Stop feeding birds until this wildlife crisis is over.

A NOTE TO COMMENTERS: Comments on this blog are moderated. If you post a comment that is profane or could inflame others, I will edit it or delete it.

UPDATE, 2 July 2021: The mysterious illness has now been reported in DC + eight states: VA, WV, MD, PA, DE, IN, OH, KY and more closely matches the Brood X cicada map though this may be a coincidence. My revised attempt at mapping the bird death hotspots, below, is just a rough idea not the whole story. i.e. Do not rely on my map!

Inaccurate map of bird death hotspots as of 1 July 2021 (markup by Kate St. John)

UPDATE from PA Game Commission, 8 July 2021 (posted here on 21 July): As of 8 July 2021 Wildlife Futures received 1,525 reports of dead birds in Pennsylvania. Roughly 25-30% (approximately 500) are likely associated with the current songbird mortality event. To date, the morbidity/mortality event appears to be targeting fledgling common grackles, blue jays, European starlings, and American robins. So far the following pathogens have been ruled out: Salmonella, Chlamydia, avian influenza virus, West Nile virus, Newcastle disease virus, herpesviruses, poxviruses, and Trichomonas parasite.

(photo from NPS via DNREC, maps from Wikimedia Commons. Click on the captions to see the originals)