The Strange Case of Blue Jay Migration

Blue Jays have been a major presence in Eliza Howell Park during the last month, the time of their fall migration. Each year I anticipate their acorn harvesting frenzy (see “Blue Jays Harvesting Acorns,” August 27, 2018) and this year they again worked the oak trees in great numbers.

Note: All bird photos by Margaret Weber

Their month-long period of intense activity in Detroit is exciting to observe, but I am increasingly aware of their unusual – and not fully understood – migration behavior.

Most birds that migrate through our area in the fall leave all or much of their breeding ground for the winter. Blue Jays, by contrast, are found in the very same areas all year round. It is interesting to compare the following two range maps. The first is White-throated Sparrow, also moving through here in September, and the second is Blue Jay. (These maps are taken from the Cornell Laboratory of Ornithology website.)

White-throated Sparrow range

White-throated Sparrows leave almost their entire breeding area in the fall.

Blue Jay range

Blue Jays are found throughout winter in the very same areas in which they breed. A few scatter to the west, but the entire breeding area remains occupied.

Such a range map usually suggests that a species is non-migratory. Blue Jays, however, migrate and do so in great numbers. Every fall the raptor counters at the two locations by Lake Erie (Detroit River Hawk Watch at Lake Erie MetroPark and Holiday Beach Conservation Area in Amherstburg, Ontario) count Blue Jays as well as raptors. As of October 10 this year, Holiday Beach watchers had reported over 350,000 Blue Jays moving through since early September. And the migration wasn’t fully over yet.

This is what is known (and/or thought likely) about Blue Jay migration, based on my review of some of the published research:

• The species is partially migratory; only some migrate
• Most that migrate go only a few hundred miles south in the fall
• It is estimated that fewer than half migrate
• Those that migrate (and those that don’t) include both young birds and older birds
• Individual birds might migrate one year and not the next and then migrate again in the following year
• The migration number in a particular year is suspected to be related to food sources

The jay numbers will soon decline in Eliza Howell as the migrants move on. But I do not know whether individual birds like this one, seen in an oak tree in September, will stay for the winter.

I do not know whether this one, nesting here in June, will be around in the coming winter

I had assumed, if I thought about it much at all in the past, that the same birds (the non-migrants) were present in summer and winter and the migrants all passed through. Now I doubt that.

One of my other questions, not addressed in the limited research I have reviewed, is whether some of the individual jays harvesting acorns in the park leave/migrate before the winter and do not ever go back to eat the acorns they hid. Is acorn harvesting possibly community and not just individual food-gathering?

The Blue Jay is a common bird, so it is tempting not to give it a second thought. But I rarely see jays these days without thinking about what I do not know about them.

An October Morning Walk: Today’s News

I arrived in Eliza Howell Park on October 9, 2018, at about 8:20 a.m. It was already warm, very warm for this time of the year, after a heavy dew. For the next three hours I walked about with my binoculars and phone camera, with frequent stops.

These are some of my observations on what is happening in the park today.

1.Sun and Dew

When the morning sun shines, it highlights the wet twigs and leaves, and the moisture rises in the air like fog. The temperature was unusual for October, but the picture is not.

2.Honeysuckle berries getting ripe.

There are many honeysuckle shrubs (Amur honeysuckle) in the park. They have lovely white flowers in the spring, but are perhaps even more attention-getting in the Fall. They keep their leaves longer than most deciduous plants and will be mostly green with abundant red berries into November. They have been ripening slowly and more are red every day.

3.Mushrooms continue in season.

I recently posted a report on some of the mushrooms in the park (October 4, 2018). Mushroom season continues and, in the last few days, there are even more to be found, in many shapes and sizes. This is just one of many I thought photo-worthy today.

4.Migrating sparrows arriving.

As I noted in another post (September 28, 2018), part of my October focus is on the variety of sparrows that pass through the park. This morning I saw six different sparrow species, including a flock of Dark-eyed Juncos and my first-of-the-season Field Sparrow (pictured here in a photo from another time).

Photo by Margaret Weber

5.Monarch butterflies are still present.

Monarchs have been in migration to Mexico for about a month now and I have been checking for them during each visit to the park to see whether there are any still present. Today I saw 4. So they have not yet all passed through, though that will happen soon.

I thought today of the Monarch caterpillar that I saw on September 12 (picture) and wondered then whether it would have time to make it to butterfly in time to head to Mexico with the others. Perhaps it is now on its way.

6.Chestnuts are falling.

Many, maybe most, of the nuts and acorns in Eliza Howell have already fallen. When mature chestnuts fall, the outside shell (the burr) opens on its own – to the benefit of squirrels and others. Many empty burrs are now on the ground under the trees. Sometimes the burrs open before they fall; this one is still on the tree, with two of the three nuts having dropped. (For more about EHP chestnuts, see post of July 31, 2018.)

7.Tree leaves are starting to turn.

Except for the species whose leaves turn red early (such as staghorn sumac and Virginia creeper), most of the leaves in the park are still green in early October. Today, however, there are definite signs that the change has begun on some of the large deciduous trees.

8.Second hornet nest found.

Bald-faced hornets often build nests in a number of trees scattered around the park. I typically see 10 or more each year, starting to spot them in late summer but finding most in the fall when they become more visible with the leaves thinning or gone. This year I had only seen one so far, a small one, found on August 17 and pictured here, and have begun to wonder whether this year might be atypical. Today I (finally) found a second one.

9.Purple love grass starting to tumble.

Anyone visiting the park in late summer or early fall is likely to notice the hue of the foot-high plants called purple love grass. When the grasses dry up, they (now brown) detach and blow across the ground like tumbleweed. Tumbling is now starting to happen. (The picture is from mid-September.)

10.Snails feeding on stems.

The terrestrial snails common in Eliza Howell (perhaps a type of banded snail) have been active since April, when they emerged from hibernation. They seem to be especially abundant right now, climbing up several feet on plant stems (they feed on both live and dead plants). Here is a collage of four I saw today.

These are some of my notes from a morning walk in the park.

 

Four Months Here, then Gone Again

Among the birds that breed in Eliza Howell Park and “winter” in or near Central America, I selected four and reviewed my records on first sighting and last sighting in the park each year from 2010 to 2018 (9 years). The dates indicate clearly that they are only short-term residents here, coming to breed, and longer-term residents elsewhere.

Note: All photos by Margaret Weber

Baltimore Oriole

I do not get to the park every day and, of course, I miss some birds when I am present. Nevertheless, the record is quite consistent. Based on this experience, I expect to see the first Baltimore Orioles of the year the first week of May and will probably not see them after the first week of September.

Baltimore Oriole 2010 – 2018

First seen:     5/6    5/8   5/2   5/5   5/6   5/6   5/7    5/1    5/4

Last seen:     9/3   8/25  9/5  8/22  9/7   9/7  9/11   9/4   9/3

By the end of May, I start finding Baltimore Oriole nests every year in the large trees, often near the road, and find a total of five in a typical year.

Barn Swallow  

Barn Swallows also nest in the park every year, at least one pair under a shelter and several under the Fenkell Avenue bridge over the Rouge River.

Barn Swallow   2010 – 2018

Fist seen:   4/24  4/23  4/19  5/1   4/17   4/26   4/22  4/29  4/25

Last seen:   9/2  8/28   8/24  8/22  8/24  8/23  8/20    9/9   8/31

Blue-gray Gnatcatcher

The Blue-gray Gnatcatcher arrival date (more exact, first sighting date) is spread over a three week period, not as consistent as with the Baltimore Oriole. The last-sighting date covers a shorter range of time. By the end of the second week of September, they have started their trip back to Central America (some to Florida) for a longer stay.

A couple pairs of gnatcatchers always nest in Eliza Howell and I have been successful most years in locating a nest to point out to participants in the June Detroit Audubon breeding bird field trip.

Blue-gray Gnatcatcher 2010 – 2018

First seen: 5/3  4/28  4/19  5/1  4/23  4/11  5/1  4/20  4/28

Last seen:  9/6  9/14   9/9   9/2   9/7   9/7   9/11   9/4   9/5

Ruby-throated Hummingbird

There are always a small number of Ruby-throated Hummingbirds that spend four month at Eliza Howell, but I have found an actual nest only once over these years. I am quite sure they nest here every year, however, based on the behavior of adults and on the slight increase in numbers by late summer. They spend the non-breeding months in Central America.

Ruby-throated Hummingbird 2010 – 2018

First seen: 5/12  5/8   5/10  5/14  5/10   5/15  5/13  5/11  5/4

Last seen:  9/6   9/5    9/9    9/14  9/14  9/13   9/16   9/9   9/22

—-

These four species are not the only birds that nest in the park and leave after breeding season, but these records may be sufficient for now.

—-

There are several points to be made based on the above records.

1. Birds that migrate are amazingly consistent from year to year. It is often possible to predict when (within a week or so) a particular species will show up again.
2. If someone wants to see any of these four species in October, don’t come to Eliza Howell.
3. This information, along with the annual fly-through of the warblers, helps to explain why many bird watchers in this part of the country go a little crazy as May approaches. By then, it will have been a long time that some favorites have been gone.

A World of Mushrooms

With most of my attention on birds, wildflowers, butterflies and other insects, I did not always look carefully at mushrooms during my walks in Eliza Howell Park. This has changed. I now stop for mushrooms, especially in September and October when they are most abundant, both in numbers and in variety.

Mushrooms, in different shapes and sizes and colors, can be found pushing up from the ground in almost any section of the park, often but not always near trees. Some have the familiar umbrella shape.

The majority are white. This collage of white mushrooms includes examples that do not have the stereotypical umbrella shape.

A mushroom is a fungus (but not all fungi are mushrooms); fungus is its own kingdom in the classification system, separate from plants. The part that rises from the ground is the fruiting body, only a small part of the much larger organism that lives underground.

I sometimes think of mushrooms as non-plant flowers, especially the colorful ones.

Mushrooms have long been hunted as food and some varieties are cultivated. Selecting naturally growing mushrooms for dinner can be risky if one does not know them extremely well; some poisonous ones look very similar to edible ones.

When I stop and look, my interest is observation, not eating. I have to admit, however, that this one, about 6 inches across, reminds me of a loaf of bread!

Most mushrooms are soft and short-lived. They are the reproductive stage of the organism; they sprout, open up, and drop their spores.

Many mushrooms have gills from which the thousands of spores (reproductive cells) drop and disperse. Picking or cutting a mushroom (which does not harm the larger organism) provides an opportunity to take a look at the gills on the underside of the cap.

Some mushrooms grow from the soil and some grow from (often decaying) wood. Those shown above are ground mushrooms. Just as fascinating are the wood mushrooms, including bracket or shelf fungus.

A look at varieties of bracket fungi in Eliza Howell is a project for another time. It was difficult enough to select/limit the pictures of the ground mushrooms here. There is a whole world of mushrooms out there!