How rare is rare? – a butterfly tale

As spring slides into summer birds go quiet; nesting, rearing their young, preparing for their southern migration or just hanging out.  I switch to Lepidoptera and Odontata to keep me busy.  Butterflies and dragonflies have elaborate life cycles; eggs become larvae which grow, sometimes over long time periods, bigger and bigger and finally transform to often spectacular adults who spend their short lives looking for mates, mating- and for the females- laying eggs to renew the cycle.

I’ve discussed dragonflies in two previous posts.  Recently however, I went in search of a butterfly that has eluded me for more than ten years.  The Pipevine Swallowtail is one of five species of Swallowtails, Papilionidae, that can be seen in the Boston area.  Perhaps the most common of this group is the Eastern Tiger Swallowtail:

Eastern Tiger Swallowtail Papilio glaucus

There are two other relatively common swallowtail species in the area; one is the Spicebush Swallowtail:

Spicebush Swallowtail, Papilio troilus, on Swamp Milkweed

It can be tricky to distinguish that predominantly black butterfly from the named Black Swallowtail:

The small yellowish/whitish single spot near the top of the forewing is one way to differentiate this female Black Swallowtail, Papilio polyxenes, from the Spicebush species

To make matters worse, there is a notable gender difference in this last species:

Note the broad yellow median band on the wings of this male Black Swallowtail, and the sub-apical spot characteristic of the species.

Early in July I went to the area where I thought I would have the best odds of finding a Pipevine Swallowtail.  Pipevines, like most butterflies, have specific plants on which they lay their eggs, so called host plants.  Most plants produce toxic substances to reduce their chance of being eaten by predators like the caterpillars of moths and butterflies.  To get around this defense, butterflies evolved over time a resistance to the toxins of one or more plant types; they aren’t deterred by the poison and in fact benefit from eating it because they in turn take the nasty toxin into their bodies thus protecting them from being eaten by birds or other predators.  Many butterflies have several host plants; the Pipevine has only one, the genus Aristolochia or Dutchman’s Pipe, named for it’s flower which is thought by some to resemble a meerschaum pipe:

Aristolochia macrophylla in bloom

The Editor of the Arboretum’s scientific publication Arnoldia has recently written a great post on her blog ARblog which describes this symbiotic relationship in detail.

The Arboretum has a number of these vines growing on the chain link fence surrounding the garage near the main entrance.  I’ve searched them every summer since I learned of the swallowtail connection- in vain.  But this time I spotted something interesting fluttering around the massive leaves of Aristolochia macrophylla:

Pipevine Swallowtail, Battus philenor, on Pipevine

Could this be my illusive lep?  A moment later it perched and I got a closer look:

Female Pipevine Swallowtail, ovipositing on Dutchman’s Pipe

The butterfly was laying eggs on a stem of the vine!  Identity confirmed!

When I returned home I tried to determine just how special my sighting was.  I went to the website Butterflies and Moths of North America and focused in on sightings in Suffolk County, Massachusetts.  There was only one historical listing in over 23 years, a sighting verified in 2004.  Another check on sightings for the entire state since 2010 uncovered only 28 reports.  I was on to a big time rarity!  I emailed some friends who work at the Arboretum, posted the sighting on MassLep (a local list server), and reported it to the above website along with some images.

A week later the Manager of Plant Records at the Arb, and fellow naturalist, emailed me an image of a Pipevine Swallowtail he caught nectaring on an azalea flower at the top of Bussey Hill:

Pipevine Swallowtail Battus philenor on Rhododendron arborescens Photo by Kyle Port

So this was now the third sighting of this swallowtail in Suffolk County?  And as if that wasn’t enough, the next day I received word that two seasoned horticulturalists on the AA staff had discovered Pipevine Swallowtail caterpillars on the same vines near the garage back in 2010, and had even over-wintered one which emerged from it’s chrysalis the following spring!  They have found one or more as caterpillars almost every year since then.  But they record stuff in botanical journals.

Suddenly my rare discovery seemed mundane.  Maybe this swallowtail was pretty common, but no one bothers to report it to obscure websites.  I backed off my high to gather some perspective.  I had never seen it, and I’ve been looking at butterflies for many years.  A cursory review of MassLep reports in the last few years revealed only 3 reports, and they were HIGHLIGHTED in each case.  So yes, this was a rare sighting, but perhaps the Arboretum, with it’s abundant pipevine plantings, may be a local mecca for this lep.  In fact, when I made a presentation on site about my find recently, one of the attendees reported he had seen what he thought might have been a Pipevine Swallowtail as he approached the meeting site.  I pointed out that other more common black butterflies were more likely.  But after the meeting some in the group went with him to where he had his sighting and found and photographed the creature.  After review, the image turned out to be our index swallowtail!  I’ve been back a number of times to follow the development of the eggs and have seen several more likely suspects in flight but have not been able to confirm their identification.

Speaking of the eggs, they have hatched:

About 20 of the 50 or so eggs that were laid by the female butterfly

Five days later most of the eggs have hatched into first instar cats.

A dozen second or third instar cats still hanging out together a few days later.

This little guy has a delineated head at one week of age, and has wandered away from the herd.

Another colleague at the Arboretum has agreed to share her Monarch caterpillar inclosure on display in the Visitors Center, and we have put about a dozen of the Pipevine caterpillars inside along with host plant offerings.  Will they pupate?  Stay tuned, or better yet, come and visit the display when you’re nearby.

The butterfly inclosure at the Visitor’s Center in the Hunnewell Building.

Four of the transplanted Pipevine caterpillars seen through the screen inclosure.

As I mentioned at the beginning of this long post, there are five swallowtail species that can be seen on the Arboretum grounds.  I still have one to go, although I did see it a few years ago while vacationing in Pennsylvania:

Giant Swallowtail Papilio cresphontes. Although this is a very poor photo, it is enough to confirm the identity of the specimen. The yellow spot within the tail, seen to the right of the lower berries, is diagnostic.

Giant Swallowtails have been reported in the Arboretum for the last two years; it is a species that seems to be increasing in our area.  Their host plants are Prickly Ash and Hop Tree; both are represented in the collection.  I’ll be keeping a look out!

Good butterflying!

A Late Migration Bird Walk


Those of you who are birders know that the spring migration in Boston this year has had its up and downs.  The lingering cold and inauspicious winds kept the migrants back, and to some extent moved them inland. Then this past week there was a sudden weather shift, and the warblers and other migrants fell from the skies!  Today’s walk in the Arnold Arboretum was back to high 50’s temperatures with unfavorable northeast headwinds.  But it was sunny and 43 birders of all ages enjoyed the beauty of the landscape and some nice birds, even though the viewing was less than optimal with trees fully leafed out.

My co-leader Patrick brought his thirteen month old daughter, in carrier, who claimed the prize for youngest.  In keeping with Patrick’s interests, her middle name is Wren!  Next youngest was an energetic five year old who liked to hold hands as we walked; I didn’t complain! We also had a teenager from New Jersey, a solid young birder who helped me locate several birds. Not surprising that he has a passion for birding; his mother’s name is Robin!

As we waited for the 8:00 AM starting gun we ticked off a stunning male cardinal in full song and a couple of Cedar Waxwings in a nearby tree:


Cedar Waxwings always look ready for a grand occasion.

We checked out feeders in two locations and found little, but our first warbler did appear, an American Redstart:


Redstarts are noisy and visually noticeable as they flit through the trees and bushes. It is one of the more common wood warblers in the spring migration, and some stay and nest here.

We heard several other warblers on our walk but got to see only one other, the Yellow Warbler.  They are just beginning to build nests in the Rose Garden section of the Arb; soon there will young to feed:


Female Yellow Warbler at her active nest.

Our only thrush on the walk gave us a bit of a puzzle.  Seen clearly on the path ahead, it had a very faintly spotted breast (not Wood), same color of back and tail (not Hermit), and no distinct eye ring or spectacles (not Swainson’s), so even though it seemed more gray-brown than rusty in low light, we settled on a Veery.


The Veery is in the thrush family and has an incredible, two-toned song.  Veerys winter solely in Brazil.

As we walked along Oak Path up to the top of Bussey Hill the group gained familiarity with the sing song cadence of the Red-eyed Vireo, but we never saw one clearly:


The Red-eyed Vireo can be distinguished from other members of this group by absence of wing-bars and the long white eyebrow and dark eye-line.  It is heard much more often than seen.

The flycatcher family was also evident on the walk. I heard a Great-crested Flycatcher but couldn’t locate it.  Eastern Wood-peewees were calling from several locations, and we finally saw one:


Eastern Wood-peewee, backlit

Sound recording courtesy of Lang Elliott NatureSound Studio

And someone in the crowd located an Eastern Kingbird at the top of a tall deciduous tree:

Eastern Kingbird

Eastern Kingbird. Kingbirds nest in the Arboretum yearly. They can be identified by their solid white breast and white terminal tail band, especially in flight.

Several birders remembered that we saw a Scarlet Tanager last year on a similar walk; they wanted a re-run. I had heard and seen tanagers on Bussey Hill twice this week, but today couldn’t produce one.  Here’s one I captured four days before the walk:


Male Scarlet Tanager. Where was he today??

The Arboretum is first and foremost a tree museum, so I couldn’t resist pointing out a famous tree in Explorers Garden atop Bussey Hill:


Dove Tree, Davidia involucrata. The other common name for this unusual tree is Handkerchief Tree, for obvious reasons when in bloom.

Ned Friedman, the Director of the Arboretum, has just written about this historic tree on his blog, check it out!  As we headed back to the main gate we passed the Black Locust near the ponds where an Eastern Screech-owl  has sunned itself most days for the last four winters.  A few months ago I posted some new information on this owl.  Was she pregnant?  Ten days ago I was coming down Meadow Road from the ponds and checked the roost hole.  I saw an owl in the hole, but when I got my bins on it it seemed different:


Eastern Screech-owlet(s).  If you look closely you can detect another eye behind and to the right of the gray bird.  Possibly the mother- or a  second baby?

About a minute later momma popped into view!


Female red phase Eastern Screech-owl

The size of our group made it hard to stay in touch with everything that was going on.  Patrick had, along with several others, heard the distant sound of a Black-billed Cuckoo.  I missed it, but we added it to our list. When the walk was finished a young couple who bird regularly in the Arboretum told me about a bird they had both studied while on the walk but couldn’t identify.  After a few questions, I showed them a photo of a female Orchard Oriole. Bingo, they both agreed that was their bird!


Orchard Orioles are much less common than Baltimore’s in the AA, but they breed here every year.  As is generally the case in the avian world, the female is much less showy than the male.

I checked off one more species.  The general rule for counting a bird is that at least two persons in the group have to have seen or heard it definitively.

The list:

Arnold Arboretum, Suffolk, Massachusetts

May 20, 2017 8:00 AM – 10:00 AM

1.5 mile(s)

60, sunny,  BBC walk

33 species

  • Canada Goose  1
  • Red-tailed Hawk  2
  • Herring Gull  2
  • Mourning Dove  2
  • Black-billed Cuckoo  1    
  • Chimney Swift  2
  • Red-bellied Woodpecker  2
  • Eastern Wood-Pewee  3
  • Great Crested Flycatcher  1
  • Eastern Kingbird  1
  • Warbling Vireo  4
  • Red-eyed Vireo  2
  • Blue Jay  3
  • Tree Swallow  1
  • Veery  1
  • American Robin  15
  • Gray Catbird  8
  • European Starling  1
  • Cedar Waxwing  3
  • American Redstart  4
  • Yellow Warbler  4
  • Blackpoll Warbler  2
  • Yellow-rumped Warbler  1
  • Chipping Sparrow  3
  • Savannah Sparrow  2
  • Song Sparrow  3
  • Northern Cardinal  3
  • Red-winged Blackbird  5
  • Common Grackle  9
  • Orchard Oriole  1
  • Baltimore Oriole  7
  • American Goldfinch  2
  • House Sparrow  4

View this checklist online at

This report was generated automatically by eBird v3 (

Looking over the reports of the five walks this spring, including one at Leverett Pond/Olmsted Park, 57 species were seen overall, by over 150 people, although many of them were repeaters.  Lots of fun for a lot of folks!  I hope to see many of you in the fall when the migrants begin their long journey back to their wintering grounds.

Good Birding!



2017 Bird-a-thon for the Boston Nature Center

On Saturday May 13th I joined two other birders for a full day of birding to support the Boston Nature Center’s Bird-a-thon (BAT) team.  The time frame for Bird-a-thon is 24 hours, and some of our team started at 6 PM Friday night; I was home cooking supper during their local excursion to Millennium Park. It’s good that they went because more than a half dozen of our total recorded birds were Friday night finds that we didn’t see on Saturday.

We left Boston at 6 AM and hit our first stop, Wompatuck State Park, before 7.  This huge park in Hingham is often a great location for migrating warblers in mid May, but the crazy spring weather has thrown the migration off.  Many of the 20 or so warbler species that can be seen there were missing.  We did get some though, including the uncommon Bay-breasted Warbler.  I have never been able to get a good image of this bird- they’re often high in the canopy- so I borrowed one from a friend who is an excellent birder and photographer:

Bay-breasted Warbler- Ted Bradford

A great shot of the striking Bay-breasted Warbler- Photo courtesy of Ted Bradford

We birded sections of this 3200 acre park for more than two hours and picked up more than 40 species, a pretty good haul in spite of the cold and dreary weather.  Some of the birds we ticked off were heard but not seen; this is one of them:


Winter Wren at Ward’s Pond on the Emerald Necklace. This tiny bird is secretive and hard to photograph.

And here is it’s lovely song:

Sound recording courtesy of Lang Elliott NatureSound Studio

We moved on to another great birding locale in southeastern Massachusetts, World’s End.  This peninsula that juts out into Boston Harbor is part of the new Boston Harbor Islands National Park.  It’s tree-lined carriage paths were designed by Emerald Necklace landscape architect Frederick Law Olmsted as part of a planned housing development, which thankfully was never built.  It is now owned by the Trustees of Reservations which will preserve it’s biodiversity in perpetuity.  Because of it’s extensive ocean front we looked for water birds, and we found some:


The perspective in this image exaggerates the size difference in the two egrets found in our area. The Great Egret, front right, is a little over a foot taller than the Snowy Egret, but size distinctions are often misleading as long necked birds appear short when crouched down searching for food.  The key to identification is the black bill and yellow “slippers” of the Snowy, compared to the yellow bill and all black legs of the Great Egret.

A species we unexpectedly saw at World’s End was a sea duck:


Male Common Eider. These salt water waterfowl are more common in winter but they have recently begun breeding in Boston Harbor

After picking up another 15 species we moved on to Ferry Hill Thicket in Marshfield, a small spot surrounded by development that was quite productive for us last year.  Not so this year; we got only one new bird there, a House Wren which we heard but never saw.

Our final stop in the south was Mass Audubon’s Daniel Webster Wildlife Sanctuary also in Marshfield.  I love this place!  It has nearly every habitat one can imagine; vast meadows and open fields, woodland, a small pond, a river and a marsh, all maintained  to suit wildlife. There are a number of “target birds” that birders seek here.  The Bobolink, an open field migrant, was abundant and very vocal; their song is accurately described as bubbly.  When seen, they stand out in the open fields:


A male Bobolink, showing his golden crown.

We also got another raptor to add to our list of five for the day, Osprey:


Ospreys arrive from the south around mid-March, and because of the installation of platforms for nest building they have become a common sight along the New England coast.

We were disappointed that the Purple Martins that are attracted to this site because of gourd nest holders had not yet arrived.  Nonetheless we added another 15 species to our growing list, and together with a number of species that we saw at multiple locations, our list had grown to 80!

We had some time left before the official end of the BAT competition when we returned to Boston, so we headed for the summit of Mission Hill.  I described this urban hot spot in last year’s BAT post; it has been very active with “good” birds this spring.  The hour was late and the wind had picked up however, so both sections of this complex were quiet. We did get a common sparrow that somehow we had missed all day, White-throated Sparrow:


Male White-throated Sparrow.  This was one of only four of the 17 possible sparrows we tallied for the BAT.

As we were heading back to the car our youngest member spied something high up in a tree.  Small, like a warbler, but chubbier and with a white eye spectacle. Blue-headed Vireo!


Blue-headed Vireo. This vireo was once lumped with two others as Solitary Vireo, but DNA studies in 199o’s lead to the three types being split into three distinct species.

So we ended up seeing three of the six possible vireos in this region.  It was a fine way to end a long day.

Overall it was a very successful Bird-a-thon. The real point of the day, after all, is to raise money for Audubon, and for the wonderful programs that the Boston Nature Center in Mattapan provides for people of all ages, especially kids.  Our small team raised over eighteen hundred dollars so far, a good share of the funds raised by BAT for the BNC. Thanks to all who contributed; if you you would like to do so now here’s a link to my giving page.

My last walk of the season will be this Saturday May 20th beginning at the Arboretum main gate at 8:00 AM.

Good Birding!