Category Archives: Hazards and Mortality

A Mite-y Big Problem at Flycatcher Nest

I dislike unhappy stories and enjoy writing about them even less. However, I have to remind myself that not everything is about the birds — Mother Nature is a much more clever scriptwriter than that.

I mentioned in my last post that there were some moving specks on the vinyl siding behind the nest that I suspected might be some kind of bird mite. Here is what my research found.

At the end I share my opinions as to the effect that the mites had on the nestling development and their departure from the nest.

Visual Evidence of Mites

I went back and looked at video footage to look for evidence of moving specks which I would later confirm to be mites. It turns out that a good way to see them is to fast-forward the video and watch closely — the mites are easy to see when moving, especially those on the light coloured vinyl siding.

I found the first mite evidence in the July 19 webcam footage — (hatch-day + 8). On subsequent days, the quantity of mites increasing dramatically, dare I say ‘exponentially’, until the three nestlings left the nest on July 23. While the initial mites were only seen while moving on the vinyl siding, by July 21 large immobile clusters of mites could be seen on the outdoor light fixture.  Here is a picture taken on July 22 with my Panasonic FX-200 camera:

Mites on the Light Fixture

Mites grouping on the outdoor light fixture.

The out-of-focus mites are still visible on the siding behind the nest. More obvious are the the brown patches on the black edge of the light fixture in which individual mites are easily visible. The reddish-brown colour comes from mites that have all taken some blood, probably from one of the nestlings (’empty’ unfed mites are light coloured).

To study the mites more closely, I ran a lint roller along the edge of the light fixture. This was surprisingly effective at removing all of the mites in its path. The sticky lint-roller paper immobilized most of the mites however there were still a number of wandering mites so I sprayed the sample with a mixture of bleach and water to make sure the mites were dead before the sample came into the house.

To demonstrate the mite size and numbers, I took a picture showing a section of lint-roller paper with mites next to a Canadian dime:

Mite Sample

Mite sample acquired using a lint roller.

A dime is about 1.8 cm in diameter so I estimate the density of mites in the high-density area along the top of the sample to be about 200 per square centimetre. After the nestlings had left the nest, there was extensive coverage of the light as well as 4 or 5 patches of packed mites on the siding. Estimating the visible coverage at around 200 square centimetres that would mean about 40,000 mites. This is just the visible areas and the hidden areas on the light fixture. Any mites on the nest or the nestlings are not included though one might expect both to be heavily infected. My best estimate for the total mite count is somewhere between 50,000 and over 100,000.

We have a Wild M11 microscope which I used to get a better look at the mites. Using my iPhone camera, I was able to take some surprisingly good pictures. The following image was taken at the lowest (4X) magnification:


The wire has a length of about 2.2 mm at this magnification (calibrated with a plastic ruler) making the mites’ length about 0.6 mm. The next image was made at the next highest magnification (10X).  Unfed mites are clear so this looks like a mite that has fed on blood — nestling blood most likely.



The two most common North American bird mites are the Northern Fowl Mite (Ornithonyssus sylviarum) and the Chicken Mite (Dermanyssus gallinae) which goes by several other names such as the Red Mite, Red Fowl Mite and Red Poultry Mite. Both are of great interest to the poultry industry because of the costly damage they can do. Both can infect wild bird species. From various sources I have read, I concluded that the flycatcher nest was probably infected with the Northern Fowl Mite.


The best reference that I found summarizing issues around bird mites and humans comes from a 2010 document from the PennState, Department of Entomology series of short Entomological Notes simply titled BIRD MITES (accessed July 28, 2017).  Below, I quote a few of the more relevant paragraphs and highlight important sections that helped me handle the flycatcher mite infestation:

Bird mites are very tiny, flattened parasitic arthropods in the order Acari. They belong to two closely related genera in two families; Dermanyssus species in Dermanyssidae (Fig. 1), and Ornithonyssus species in Macronyssidae. Bird mites have piercing mouthparts that enable them to take blood meals from their bird hosts. Although the mites will inadvertently bite people, they cannot reproduce without their bird hosts.


Bird mites have five stages: egg, larva, protonymph, deutonymph and adult. The larvae have three pair of legs; the nymphs and adults have four pair. Adults are about 0.7 to 1 mm in length and are just barely visible to the naked eye. Unless they are moving, they are extremely difficult to see. The color is translucent white until they take a blood meal after which the mites are reddish mahogany to brown. Mite eggs are white, oval and cannot be seen without the aid of magnification. The same applies to the larvae and nymphs.


Most bird mite species can complete development in five to twelve days with optimal temperatures and host presence. This short life cycle makes it is possible for mite populations to attain tens of thousands of mites in bird nests during the rearing of young birds. If the population is too large (or if the fledglings vacate the nest or perish), the mites will migrate in mass to locate an alternative host. It is during this migration that mites can and do enter the living quarters of people. Some mites (i.e. Dermanyssus gallinae, the chicken mite) can survive for several months without taking a blood meal; the northern fowl mite, Ornithonyssus sylviarum, for several weeks. However, the mites do not appear to survive for more than several days in the reduced humidity (<35%) environs typically found in air-conditioned or dehumidified homes.


Birds should be discouraged from building nests in or adjacent to buildings. Close all openings large enough for birds to enter attics, sof ts and similar areas. Install hardware cloth, sheet metal, or other materials to prevent birds from nesting and roosting on porches, breezeways and other exterior sites. Disrupt nest-building efforts by removing partially completed nests in shrubbery and on air conditioners and windowsills.

If mites are detected in the structure, locate the bird nest source. Remove the nest.

My take home message was to monitor the mites both around and away from the nest and be prepared to remove the nest and sanitize the nest area once the nestlings had left the nest to prevent the host-less mites from moving inside the house looking for new targets. I read some accounts of the problems that resulted from houses that became infected by bird mites (readily available on the websites of many extermination companies) and they definitely made me want to keep the mites outside.

Of Mites and Nestlings

Beside the visual evidence of an exploding mite population, the nestlings became increasingly restless as the quantity of mites increased. Frequent episodes of scratching were noticeable on the webcam videos.

My personal belief is that the nestlings left the nest early, before the were ready to fledge, in large part because of their discomfort from the mites. I know that one nestling perished because I found the body on the morning of July 24. The last sighting of a nestling was on the morning of July 25. The last sighting of the female adult sticking close to its foraging area near our house was on July 25.

One final reason why I do not think that there were any surviving nestlings was the presence of a domestic cat nearby. The day that I found the dead nestling, it was lying in our driveway when I returned home from some errands. I have seen the cat, before and since, in and around our yard. An unfledged nestling hopping in the bushes would have had little chance of avoiding the feline if it were spotted.




I have listed below some of the interesting references that I found online.

[1] This 2005 reference contains some good high-level information on mites: Common Lice and Mites of Poultry: Identification and Treatment.

[2] One of the best short summaries on bird mites that I have found: UW Madison Department of Entomology information sheet.

[3] Good reference from Iowa State University: Bird-Mites.

[4] A good 2014 review article: Mites and birds: diversity, parasitism and coevolution.

[5] A 2014 research article looking at some of the relationships between birds and mites: Repeatability of Feather Mite Prevalence and Intensity in Passerine Birds.
[6] Slides from a presentation showing the Poultry Industry’s views on Northern Fowl Mites.
[7] Washington State University research proposal and status: ORIGIN AND SPREAD OF THE NORTHERN FOWL MITE: A LANDSCAPE GENETICS APPROACH.
[8] Google Books textbook chapter: Global Diversity of Mites.
[9] Countryside Daily article with some information that I did not find elsewhere: Chicken Mites & Northern Fowl Mites: Controlling Infestations.

Pacific-slope Nestlings 10 Days Old

July 21: As of yesterday the Pacific-slope Flycatcher nestlings are 10 days old. Their eyes are opening and feathers are starting to show. They also appear much more restless than in previous days and I’m a little worried that one might fall out of the nest. It’s more than 6 feet down to the concrete steps so a fall would, I imagine, be fatal.

The adult birds spend most of their time foraging and only at the nest for a few seconds every few minutes. So, I thought that I’d try to get a better between-visits picture of the nestlings with my Panasonic FZ-200 camera whose 24x optical zoom lets me fill the image whereas the Logitech 920 webcam, used for my videos, has no optical zoom so cropping is the only way to “zoom in” and that results in a lower resolution image. Here is the best picture that I was able to take:


I had just focussed on the nestlings, who were alone in the nest, when the adult male flycatcher appeared in the foreground. Because of the low-light I was using a large aperture with poor depth of focus which put the adult bird slightly out of focus. It’s a nice subtle effect.

The camera picture also highlights something else not so nice. If you look closely at the vinyl siding behind the nest you can see a number of small black specks. Reviewing the webcam videos shows that these specks are actually moving around. They are concentrated around the nest suggesting that they are some form of parasite associated with nest and birds. I reviewed previous days’ videos but July 21 was the first day that the specks were visible. My suspicion is that they are bird mites which Doctor Google tells me would not be a good thing. More research needed.

Watching a Family of Palila on the Big Island

[Updated December 10 2014 based on feedback.  Additional links on the Palila have been added.]

A recent week-long vacation took us to the Hawaiian Islands (October 26 to November 1). Having previously been to the island of Kauai at the old end of the island chain, we decided to try the island of Hawaii at the other, newer end.  To prevent confusion with the state of Hawaii this is frequently referred to simply as the Big Island.  I had my Panasonic FZ-200 camera along to document the trip.

On the last full day, I signed up for a Rainforest and Dryforest Birding Adventure tour — a day-long outing put on by a tour group called Hawaii Forest and Trail.  They do many other tours too that are not just for birding.  The rest of our group, for instance, went on the Mauna Kea Summit and Stars Adventure trip which takes you up to the volcano’s summit to watch a sunset.

Our trip set out in search of 2 specific target birds.  In the dry forests on the side of Mauna Kea we would be looking for the Palila, a critically endangered species which lives in a single forested area on the volcano’s slopes.  This forested area is the source of the māmane plant which the Palila has adapted to be able to eat and which is toxic to other birds.

In the second part of our excursion, we would travel to some wetter forests where we hoped to find different endemic, the ʻAkiapōlāʻau.

While we were, unfortunately, unable to track down the ʻAkiapōlāʻau, we were extremely successful with the Palila and the rest of this article describes that encounter.

Mauna Kea and the Palila

First, a quick note and the Palila habitat on the slopes of Mauna Kea.

Mauna Kea is still considered to be an active, though dormant, volcano and even though it has not erupted in 4600 years there is still the slim possibility that a lava flow from a future eruption could wipe out this habitat leading to their extinction.  While this might make for a good story in Hollywood, the reality is that there are much more dangerous risks that could well see the Palila gone from these slopes long before they are touched by lava.  Forest fires, for instance could, in the right conditions, very quickly destroy the Palila habitat.  Other threats include introduced species of plants, animals, insects and disease.  The Hawaiian government’s Mauna Kea Forest Restoration Project has lots of good information here.  Finally, according to BirdLife International, the endangered status of the Palila in recent years is also related to rapid population declines as a result of drought that has affected its primary source of food, the māmane plant.

The Palila Plan

The plan was simple.  We parked in an area accessed by a hunter access road on the lower slopes of Mauna Kea.  The trip organizers allowed for up to 4 hours climbing the slopes to find and view the Palila after which time, win or lose, we would head for the second location.

Here is a picture taken near our parking spot and at the lower edge of the area expected to contain the Palila.  Note the sparse trees on fairly open grassland.Mauna Kea slope forest home of the Palila

Here is a second shot taken as we climbed a little further up the Mauna Kea slope.Mauna Kea slope Forest Home to the Palila

Found:  A Family of Palila

According to the guide, on one recent trip they spent most of the allocated time hunting for the Palila and only found them as they were about to quit and move on.  We got lucky and found one after about 15 minutes with another pair showing up shortly thereafter.  In fact it appears that we had found a family unit with male, female and juvenile foraging together.  The juvenile showed typical begging behaviour with fluttering wings and an adult was doing the foraging and feeding of the juvenile though regurgitation as described, for instance, in a Palila wikipedia article.  This article says that both adults will regurgitate to feed the young in our case the male was feeding while the female stood guard, presumably looking for predators.  If the wikipedia article is correct then perhaps they take turns feeding and guarding or perhaps the guarding behaviour only happens occasionally, for instance when a large number of two-legged, orange-vested homo sapiens are also foraging in the area.

If we only consider predators seen historically before the arrival of man on the islands the most likely candidates would probably have been the Hawaiian Short-eared Owl (Pueo) and the Hawaiian Hawk (ʻIo).  It is not clear what threat we birders posed to the Palila though it was clearly not enough to drive them away.  Whether or not the female would have stood guard where and when she did if we had not be there is unclear.

As mentioned earlier, introduced predators are currently one of the Palila’s biggest threats.  These include feral cats and black rats (see for instance this article on the Palila from BirdLife International (  Mosquitos transmitting avian malaria have also proved very dangerous to the endemic populations of birds.  They are also threatened by habitat degradation especially if it affects the growth and spreading of their primary food sources, the peas from the seed pods of the māmane plant and certain types of caterpillar.  Introduced mammals such as sheep and pigs are particularly bad for disturbing the forest plants.  Through hunting and fencing the threat of these has been reduced.

First Sighting: An adult male processing a māmane pod.

Our first sighting of a Palila was that of an adult male who was processing a māmane pod in the middle of a bush that provided the bird with some protection.  The following 7 pictures, shown in the order that they were taken, cover a period of about 9 seconds.  All of these pictures were cropped from the original size of 4000 x 3000 down to about 1200 x 800.  The displayed images below are shown at a resolution of 640 x 400 though the full-sized cropped images can be viewed clicking on the image and following the link back to Flickr.

P1130094 - cropped

P1130095 - cropped

P1130096 - cropped

P1130097 - cropped

P1130098 - cropped

P1130099 - cropped

P1130100 - cropped

Video of the Male Foraging

The following is a short video that was taken starting 10 seconds after the last picture (above) was taken.  You can hear the group leader describing the bird to some of the birders that were just then discovering it for the first time.  Initially you can see the Palila alternating between working on the māmane pod and raising it’s head up to check its surroundings.

You can also hear the Palila in between the periods where it is working on the māmane pod and also after it appears to be done having released the māmane pod.  Perhaps these calls were communications to the other family members that would be showing up in the seconds that followed the video.  There may even have been a specific message to the juvenile that he (the adult male) was full and that it was time to eat.  This might also explain why he dropped the pod.  It’s not clear why they moved to a different location for the feeding.  Perhaps it was because of our presence or perhaps because it is generally safer to keep moving.

Unfortunately there is a half minute gap between this series of pictures and the next series with adult feeding juvenile.  The only thing that I recall from this period is that the juvenile and adult female arrived to join the adult male and then the female left again.

Second Sighting:  A juvenile begging and being fed by the adult male.

The second set of 7 images were taken over a period of 13 seconds starting 63 seconds after the last picture in the first set or about 38 seconds after the end of the short video.  As mentioned, in these 38 missing seconds the male moved to a different perch and a juvenile and an adult female flew in to join the adult male.  Only the juvenile stayed to be fed by the adult male while the female flew off to, it appears, stand guard (see the third sighting section below).

The sequence between the adult male and the juvenile clearly shows the begging behaviour as well as the regurgitation and transfer of food from adult to juvenile.

P1130102 - cropped

P1130103 - cropped

P1130104 - cropped

P1130105 - cropped

P1130106 - cropped

P1130107 - cropped

P1130108 - cropped
The final image was taken 5 seconds after the previous one and shows the juvenile left alone and somewhat hidden in the foliage while the adult male had moved on, perhaps to start a new cycle of processing māmane pods prior to the next feeding cycle at which point he would call the juvenile to join him there.

Third Sighting: An adult female on guard duty.

The third set of 5 pictures were taken over a period of 24 seconds starting 18 seconds after the last image in the second set.

The adult female Palila, which made a brief appearance off camera took up a position 100 feet or so from where the other two birds were positioned.  Her perch at the top of a bare branch gave her good visibility. She chose a bush that kept all of the birders, which had broken into several groups by this time, on one side of her, perhaps in order to be able to see all of them at once without continually having to look in opposite directions.  As the photos show, she still does look away from time to time, perhaps scanning for other possible threats.  As mentioned previously, the two historic threats where probably the Hawaiian Short-eared Owl (Pueo) and the Hawaiian Hawk (‘Io).  At this point in our trip we had already seen 5 of these owls hunting (one near where we found the Palila) and we had one unconfirmed hawk sighting.

P1130112 - cropped

P1130113 - cropped

P1130114 - cropped

P1130115 - cropped

P1130116 - cropped


I was impressed by the fact that both adult Palilas were caring for what was clearly a juvenile bird.  The splitting of the task of feeing the young was split into roles of foraging and standing guard.  It would have been nice to know if they switched roles from time to time.  Many species, particularly migratory ones, leave their young to fend for themselves at a much younger age or only one of the adults take responsibility for the young.

 Final Thoughts

I acquired my Panasonic FZ-200 camera to help with bird identification but on several occasions it has proven useful in seeing behaviours that I would never have noticed using just binoculars.  The ability to capture large numbers of pictures and even videos with sound provides the opportunity to analyze different aspects of bird sightings that happen too quickly in the field.

It would seem that my camera is rapidly replacing my binoculars as my primary birding equipment.  Here are some things that I might change in the future that might lead to better results:

  • Take more pictures and make more use of burst mode.  You can always delete them later.
  • Take more video clips.  Images can be extracted from these videos though not with the same resolution.  Video also records sound which can be useful in understanding bird behaviour.
  • Bring a tripod.  A remote control cable might be useful as well for the still shots.
  • Make sure that the memory card is fast and has lots of space.  Bringing extra fast cards will encourage taking lots of pictures and videos.
  • Add a directional microphone that plugs into the audio in jack on the camera.
  • Get more people involved.  It would be interesting to see if better behaviour could be captured with a coordinated group of birders taking pictures and videos together.  The camera clocks would obviously need to be either calibrated or synchronized to help determine the order of various events.

It was a fun way to get introduced to a new bird and, while it took a lot of time post-processing, it was definitely more satisfying than a brief sighting and a simple pencil mark on a checklist.

For More on the Palila Check Out the Following Links

The Palila article on Wikipedia.

The Palila Status at BirdLife International (

The Mauna Kea Forest Restoration Project website from the Hawaiian state government has much more detailed and accurate information on current status and threats to the Palila.

The Facebook page for “A Paradise Lost”, an animated movie about the Palila directed by Laurie Sumiye.

Greater Sage-Grouse Granted Emergency Protection Order in Canada

GreaterSageGrouse 256x204
By Pacific Southwest Region U.S. Fish and Wildlife Service from Sacramento, US (Greater Sage GrouseUploaded by Snowmanradio) [CC-BY-2.0], via Wikimedia Commons

This story was brought to my attention through a post on the BCVIBIRDS forum.

Earlier this month the Greater Sage-Grouse, now almost extirpated from Canada, was granted a first ever emergency protection order by the federal government.  One direct effect of this order is that a number of existing and planned oil and gas projects will be either curtailed or preventing on some 1700 square kilometers of provincial and federal crown land in both Alberta and Saskatchewan.

While an important precedent for species protection, it is not clear that this order will be in time to save the Canadian populations of Sage-Grouse.  The numbers in Canada are currently estimated at around 100 birds, down by as many as 25 from the year before.

In the US there is still a significant population but, at least in some areas, local populations are decreasing rapidly mostly due to habitat loss.  The US government is considering listing the Greater Sage Grouse as endangered in both Nevada and California.

References and Further Reading

Nature Canada, Endangered Species, Species Spotlight: Greater Sage-Grouse.

Nature Canada, Newsroom, 2013-12-04: Nature conservation organizations across Canada applaud emergency order protecting endangered species, caution more action is neededNature conservation organizations across Canada applaud emergency order protecting endangered species, caution more action is needed., 2013-12-04:  Federal Government Gazette with original order.

Associated Press,, 2013-10-25:  Feds propose listing sage grouse sub-population as threatened, angering energy developers.

Schroeder, M. A., J. R. Young and C. E. Braun. 1999. Greater Sage-Grouse (Centrocercus urophasianus), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online:; doi:10.2173/bna.425

Bob Weber,, 2013-12-04: Sage grouse protection plan released.

Golden Eagle Wind-Farm Story With a Happier Ending

Young Bald Eagle over McDowell Sonoran Preserve

Young Bald Eagle over McDowell Sonoran Preserve, Scottsdale AZ, November 2013

I first found this story – US firm Duke Energy pays out over wind farm eagle deaths – on the UK raptor site: Raptor Politics.  If you do a search you will find this story widely reported around the world.

The NPR article – Duke Energy Pleads Guilty Over Eagle Deaths At Wind Farms – has a long list of comments which are entertaining to read.

From the Great Falls Tribune (Montana), this article – Duke Energy pleads guilty to killing eagles at wind farms – which has some data on similar fines paid by oil companies in the past for infractions of the migratory bird treaty.


The September  2013 issue of the Canadian online journal Avian Conservation & Biology features a number of short research articles associated with Quantifying Human-related Mortality of Birds in Canada.

Individual articles deal with the contributions from specific industries and activities including:

  • Vehicle Collisions
  • House Cats
  • Marine Commercial Fisheries
  • Offshore Oil and Gas Production
  • Industrial Forestry
  • Collisions with Buildings
  • Mowing and Other Operations in Agriculture
  • Oil and Gas Exploration in the Western Basin
  • Collisions and Habitat Loss from Wind Turbines.

All of the articles can be freely viewed online or by downloading a PDF version.

So, which one of the above categories do you think is the biggest contributor towards bird mortality?

The final article, A Synthesis of Human-related Avian Mortality in Canada, puts all the different sources of bird mortality into context.  Table 3 in this article shows bird mortality estimates separated by source and split into the categories of landbird, seabird, shorebird, waterbird and waterfowl.

And the biggest bird killer?  It is, by a long shot, the house cat with an estimated 135 million birds (almost exclusively landbirds) of which 80 million are attributed to feral cats and the remaining 55 million to the domestic variety.  Compare these numbers to the total of 186 million dead birds per year and we have house cats killing over 70% of all birds killed from human-related causes.

There’s a whole lot of interesting information in this issue.  Well worth a read.