"What is a Newfie robin?"
That's a good question. "Newfie" stands for Newfoundland Robin, also known as Black-backed Robin. The scientific name given to these is nigrideus. Those names should lead to google success but also could lead to confusion because there are questions about just what these black-backed robins are.
From a birding perspective, the only birds that can be identified as Black-backed Robins in the field are adult males. As often happens when we name something there is a natural expectation for the thing to be discrete and identifiable. In this case, not only is the definition of the thing uncertain, but the characters that birders use to identify them seems to be fairly loose and uncertain.
To get everyone on the same page, it might be good to photograph and/or carefully describe birds thought to be "Newfie" robins so that we can compare what we are talking about. We might find that there is a whole gradation of intermediates from gray backed males to black-backed males. Or we might find that people are not using the same suite of characters and that some birds don't fit and others really do.
The subspecies name nigrideus was first introduced in 1939 by James Aldrich and David Nutt (http://www.biodiversitylibrary.org/page/39689287). They called them "Black-backed Robin" based on a few breeding specimens from e. Newfoundland. If you read their paper carefully, there are a number of characteristics described, and it would be useful if everyone looking at robins tried to assess all of them together. If we are to call anything a Newfie robin, it has to conform to this description or the specimen upon which the name is based.
The confusion: Within ten years of Aldrich and Nutt's description, questions about the validity of the subspecies were raised by Austin Rand, who found birds far from the defined range (Labrador and Newfoundland) mixed with typical eastern American Robins as far as the Mackenzie River (Rand 1948 https://sora.unm.edu/sites/default/files/journals/auk/v065n03/p0416-p0432.pdf). Robert Mengel in his careful work on the birds of Kentucky noted that breeding robins in the Applachians exhibited characters of black-backed Newfoundland birds. He also suggested a gradation from typical robin to black-backed robin. (Mengel's entire book is free at the following link [discussion of nigrideus is on page 360] it's a big file! https://sora.unm.edu/sites/default/files/journals/om/om003.pdf).
Subspecies are supposed to possess roughly the same characters over a discrete geographic range blending only at range boundaries. Rand's and Mengel's observations suggested the black-backed form is not tied to a discrete range and therefore not worthy of a name. Hence, using Newfie Robin, and the implied "they're from Newfoundland" moniker, could be misleading. The black-backed birds could be local breeders or from someplace else. David Sibley notes that he has seen a similar gradation (http://www.sibleyguides.com/bird-info/american-robin/). What I'm unsure about is whether he and others are carefully assessing a suite of characters together for birds breeding outside the supposed range of nigrideus. Other workers have supported the original findings (e.g. Allan Phillips, Burleigh, Peters, and others), so it is puzzling.
Whatever they are, black-backed robins are cool to look at and fun to find. I have never seen more than a couple in flocks of robins. David Sibley says he has seen at most three at once. This leads me to think we need everyone to get on the same score sheet regarding characters. Seeing more than a couple in one flock really should be documented in some way, the validity of the name aside.
To get us thinking about what exactly a Newfie or Black-backed Robin is, let's look at some photos. The Maryland rare records committee has a helpful specimen comparison on page 34-35 (http://www.mdbirds.org/mddcrc/pdf/rcskins2011.pdf). This compares a male known to be from the Newfoundland breeding population to a typical American Robin from the Southeast. Note how the Southeast bird shows short cowl of black extending into the upper back. This is normal in many eastern robins. That doesn't make it a Newfie, but I think many birders think it does.
Here is a photo by Tom Johnson of a bird fitting the characters described by Aldrich and Nutt, including the wings and tail being more blackish (http://www.flickr.com/photos/bonxie88/8842277031/) and the contrast between the black head and back minimal. It seems that a number of characters correlate in darker birds--they all have darker more ferruginous underparts, darker (blacker) wings and tail, more black in throat (restricted more to the center of throat with black stripes broader), smaller white eye arcs, and black extending over most of the back and scapulars. (This could mean they are a morph.) As shown in Tom Johnson's photo, the feathers on the back and scapulars are pale edged, imparting a vague scaled appearance. This is another trait that typical of these birds. Here is a photo by Trevor Persons of a bird in Maine that more or less fits what we might call "nigrideus" (http://www.flickr.com/photos/trevorpersons/6954550487/). Here are some photos I took in Fairfield (https://www.icloud.com/photostream/#A3JtdOXmJp3Q4V).
These examples at least show birds closer to the original description of Black-backed (Newfie) Robin. Are they merely extremes of a broadly overlapping grade, or are they something else? If the the same characters are more or less consistent, then are they a morph more prevalent as a percentage of a population in the Canadian Maritimes? Another character that reaches extreme in Newfoundland birds is tarsus length. They are big and long-legged. They may be big and share that character over a fairly definite range, but the problem is that not all Newfoundland breeding males show the black back. According to folks there, perhaps only a fifth show the black back. This reinforces the idea of a morph (perhaps together with individual variation that comes close or overlaps). Last year Doug Hitchcox and I went through all the robins collected on Newfoundland in summer at the Museum of Comparative Zoology and found many typical male robins. Even if cursory, that's a problem for the idea nigrideus represents a discrete geographic breeding population.
From an eBird perspective, birders can enter Black-backed Robins (nigrideus). Be prepared with those photos and descriptions, even if the subspecies isn't valid, that doesn't mean we can't put a name on these birds and track their occurrence.
Good birding!
Louis Bevier
Fairfield
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