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Yellow-rump Exposed

One of the most common warblers anywhere in North America is the Yellow-rumped Warbler. When we lived down in California the “butter-butt” was one of the species that you expected to see all winter and even, in some pockets, year round.  Here on Vancouver Island it is a summer bird that will show up migrating in the spring and fall and in numbers that make it a common sight, perhaps the most common warbler seen in North America.

Many birders probably will not pay much attention to this common bird.  Look at the rump — if yellow checkmark beside Yellow-rumped.  Want more detail? Look at the throat.  If it’s yellow it’s an Audubon’s with normal western range from the Pacific to the Rockies and north to Haida Gwai.  If the throat is white, it’s a Myrtle with range just about anywhere in North America.  Oh, Audubon’s and Myrtle are sub-species.

Here are some adult Yellow-rump pictures taken in Nanaimo recently (July 3, 2019).

First, a side view.  Note the yellow markings on the throat, top of head and shoulder.

P1190832 Yellow-rumped side view.jpg

Next,  a view more from the front.

P1190835 Yellow-rumped front-top view.jpg

The throat marking is yellow for the Audubon’s sub-species seen on the west coast. On the east coast the Myrtle is more common with its white throat patch.

P1190833 Yellow-rumped front view.jpg

Of course I had to have at least one picture from behind of the yellow butt, er rump.

P1190834 Yellow-rumped back-butt view.jpg

In Disguise

At this time of year, early summer, the new batch of birds are hatching, fledging and showing up with all the other birds making bird identification trickier.  These new birds would be unrecognizable to anyone who has only ever paid attention to adult birds.  For instance, look at the following picture taken on July 11 2019:


It doesn’t look much like a Yellow-rumped but it turns out that this is in fact a juvenile Yellow-rumped Warbler (thanks to those who helped me with the ID).  There is no evidence of the yellow patches seen in an adult.


Juvenile Yellow-rumped Exposed

Look at the next sequence of 4 images, all of a single juvenile Yellow-rumped, taken over a period of a few seconds on July 14, 2019.  How do I know this is a “butter-butt”? Look at the second picture taken a few seconds after the first.

Yellow-rumped Warbler juvenile

Nothing? Don’t see it?  Look at the third picture taken a few seconds after the second:

Yellow-rumped Warbler juvenile

The bird has adjusted its feathers to show the yellow-rump.  Finally, a few seconds later still:

Yellow-rumped Warbler juvenile

The bird’s identify has been fully exposed despite the lack of any of the other yellow patches.

Nature rarely does anything without a reason which makes me wonder what purpose the yellow-butt and the ability to expose it play in the day-to-day of this warbler.  At least it makes identifying the juvenile birds without any other yellow markings a little easier.

Final Thoughts

The Audubon’s and Myrtle sub-species were separate species until 1973 when scientists combined them.  Better DNA evidence suggests that perhaps they should be separate species after all.  Check out the following 2016 article by Hugh Powell in All About Birds, an online free resource from the Cornell Lab of Ornithology: Goodbye, Yellow-Rump: Will We See A Return To Myrtle And Audubon’s Warblers?



Updated July 12, 2019: Added a ‘See Also’ section.

Empidonax: from the Ancient Greek empis for “gnat“, and anax for “master”.

Empidonax Flycatchers

Anyone who regularly watches birds in North America will, at some point, come across  a small flycatcher from the genus Empidonax for which species identification may have proven to be difficult or impossible.  In many cases the only reliable identification requires hearing the bird’s song which is only sung by the adult male and usually only during breeding season.

But wait, there’s Contopus.

There is a second genus of flycatcher, Contopus, (pewees and wood-pewees) that should be considered as some of its species can resemble those of Empidonax. On Vancouver Island the relevant Contopus species are the Olive-sided Flycatcher and the Western Wood-Pewee.

My Identification Challenge

Our house backs onto a small pond and wetland decorated with fairly heavy brush that provides good cover for birds and other critters.  The brushy area behind our yard is where I recently encountered the flycatcher shown in the following pictures:


These images were all taken with my Panasonic FZ-200 camera and have not been edited other than to crop the images. No song or call was heard from the flycatcher.

None of the Contopus flycatchers appear to be a match leaving us with Empidonax.  Based on the Sibley Guide to Birds (2000 edition) the only Empidonax species that we should see in the Nanaimo area are Pacific-slope, Willow and Hammond’s. The Least, Dusky and Gray Flycatchers have normal habitats that come close to Vancouver Island and should not immediately be discounted when comparing species based on appearance.


I am not comfortable assigning my flycatcher pictures to any of the above mentioned Empidonax species to I will solicit birders out there to propose a species type for the above images hopefully with an explanation for their identification.

See Also

Here are some resources for flycatcher identification.  I will update this post if I find additional interesting links.

Identifying Flycatchers on their Wintering Grounds

If you think that identifying the Empidonax and Contopus flycatchers is difficult up here in Canada and the US during breading season, consider what it must be like in April and May in South America where migratory species from the East and West coasts of North America are intermixed with non-migratory resident species.  To make matters worse they various species may be silent, not singing those songs that are sometimes the best way to separate and identify flycatchers.  Here is a link to a document provided by eBird Central America that will give you a summary of the ID challenges and provide you with tips on how to separate: Flycatcher ID challenges in a Central American context.

Cedar Waxwings are also Flycatchers!

P1190890 Perched Waxwing extra long

Our back deck overlooks one end of a wetlands that eBird identifies by the hotspot Oliver Woods Community Centre Pond. This location, which has only been identified as a hotspot since February 2019, has more than 50 species associated with it.  I have seen most of these from the comfort of our back deck.

In the last few days Cedar Waxwings have caught my attention. There appears to be a resident population of ten or twenty Waxwings that hand out around our end of the pond.  I usually think of this bird as hanging around in flocks looking for berries to gorge themselves on, particularly in the winter months.   I would normally expect them to be somewhere else right now.  According to the All About Birds information for the Cedar Waxwing, however, this region has year-round populations. of Cedar Waxwings.

In the last few days I’ve seen two interesting Waxwing behaviours.

First, a number of the birds regularly spend time on top of the large lily pads that cover much of the pond. They appear to be foraging for insects.  The following picture shows an example:


I noticed the second interesting behaviour at dusk.  Here is a picture of the pond just before sunset.P1190870 Pond at DuskThe glowing areas are some bushes catching the last daylight.  The glow is also attracting lots of flying insects.  The Cedar Waxwings were attracted to these insects and were making short excursions from nearby perches to fly-catch.

Here are a some images of perched Waxwings between foraging flights:P1190872 Perched Waxwing 1P1190877 Perched Waxwing 2P1190880 Perched Waxwing 3P1190884 Perched Waxwing 4

I will have to try making short videos of the fly-catching flights.

I did a little more research into Cedar Waxwing behaviour.  From the Food section of the All About Birds website Life History for the Cedar Waxwing I found the following:

Cedar Waxwings feed mainly on fruits year-round. In summer, they feed on fruits such as serviceberry, strawberry, mulberry, dogwood, and raspberries. The birds’ name derives from their appetite for cedar berries in winter; they also eat mistletoe, madrone, juniper, mountain ash, honeysuckle, crabapple, hawthorn, and Russian olive fruits. In summer Cedar Waxwings supplement their fruit diet with protein-rich insects including mayflies, dragonflies, and stoneflies, often caught on the wing. They also pick items such as scale insects, spruce budworm, and leaf beetles directly from vegetation.

I also checked Birds of North America Online (requires a subscription) and found the following text:

One of only three species worldwide in the family Bombycillidae, the Cedar Waxwing is named for the red, waxlike tips on the secondary flight-feathers of adult birds. Sugary fruits dominate the diet of this bird, especially in winter. During warmer months, Cedar Waxwings glean insects from vegetation or snatch them from the air in sallies from exposed perches, often near streams or ponds. This is a true frugivore, assimilating nutrients from fruit pulp and passing seeds intact back to the environment.

Apparently this is all normal behaviour.  Huh!

See Also:

All About Birds Cedar Waxwing Gallery

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 Flycatcher Nest

June 26: This was the day that we noticed the nest being built on top of the light in our front entry way. Our first thought was a swallow because we have a lot of them flying around our neighbourhood though most would have nested weeks earlier.

June 28: We noticed a bird sitting on the nest so I got out my camera and we discovered a Pacific-slope Flycatcher (whose 4-letter species ID is PSFL) sitting on the nest. Here is the picture that I took:

PSFC Nest P1180287

Consulting with Birds of North America Online (BNA-online) I discovered that first broods occur in April or May but some pairs will attempt a second nest around June or July. This was clearly round 2 for these birds.

June 30: I got up on a step-stool, held my iPhone 4s above the nest and took a picture:


The PSFL was sitting on 3 eggs. Consulting BNA-online again I found out that the most common number of eggs is 4 followed by 3 so we might have a full nest or there may be more to come.

July 2: Only 2 days after the first picture, I took a second and discovered that there were still 3 eggs.

July 5: Another 3 days and there were still only 3 eggs to the bird sitting on the nest was probably incubating the eggs. BNA-online indicated typical incubation periods of 13 to 16 days so, assuming that my first ‘egg picture’ indicated the start of incubation then we should expect the eggs to hatch between July 12 and 15.

July 11: A picture from my iPhone shows that the eggs have hatched:


The three ‘grubs’ in the nest look pretty helpless so they must have hatched quite recently.  I decided to call July 11 hatch-day 0.

Here is my first video of the adults coming and going, bringing food to the nestlings.

There will be many more videos and pictures to come as the nestlings grow up and fledge. I just hope that they all make it to fly away risking the odds of survival which are not in their favour — I’ve heard that only about one in ten birds survive a year after hatching.

Unexpected Finds at Buttertubs Marsh

I was birding Buttertub Marsh with a friend last Thursday (November 17, 2016). We were scanning the almost empty pond for waterfowl when Leonel noticed 4 Great Fronted Geese hanging out with some Canada Geese at the far side of the pond. It was the first time that I had seen them there.

Here’s a picture captured with my Panasonic FZ-200 at maximum zoom. It’s cropped as well. You can also see a bird in front just to the right of centre with a neck-band as well. I’ll say more on this guy later.

GWFG at Buttertub Marsh

Four Greater White-fronted geese mixed with some Canada Geese at Buttertub Marsh on November 17, 2016.

About and hour and a half later we were just about done and noticed the Canada Geese swimming more in the middle of the pond without the GWFG. It was Leonel’s good eyes and my FZ-200 to the rescue a second time. The 4 geese were across the pond on the edge of the pond resting, their coloration blending in well with the background reeds.


VIU Canada Goose Project

I said that I’d come back to that Canada Goose with a neck band in the first picture.

A group from VIU, headed by student Stew Pearce, banded 200 Canada Geese earlier this year and has been following the locations where they have been seen since using information sent in by birders or anyone else interested in helping out. The goal is to learn how the birds move about during the year. You can find out more by going to the VIU Canada Goose Project web-site.

Stew told me recently that geese from the project have been seen and reported from as far away as Portland, Oregon. So, if you happen to see a Canada Goose with a neck band let Stew know using the instructions at the above link.

So, did I figure out what the ID of our find was? Yup! We saw the bird swimming behind some reeds an hour or so after our first encounter and I took a some pictures as the goose swam in and out of view. One of the four was clear enough to ID the goose:



Our goose’s ID was “096P”. I checked the web-site and discovered that the most recent sighting was November 6 at Buttertubs Marsh. I’m guessing that this guy is not going South this winter.



This is a follow-up to a previous post summarizing the September 2013 issue of Avian Conservation & Ecology that features several articles with the theme of human-related bird mortality in Canada.

A thread on one of the birding groups that I follow was discussing the effect of wind power on birds and one of the contributors pointed to the Barnard on Wind web site (creator: Mike Barnard).  More specifically they referenced the article: How significant is bird and bat mortality due to wind turbines?  This article, along with its extensive list of references, contains a wealth of information for anyone interested in understanding the effects of wind-power on bird populations.  One of the references in Mike’s article is, in fact, the same article on the effects of wind-power that is referenced by the September issue of Avian Conservation &Ecology.

It’s a great and informative site that’s definitely worth a bookmark.