Separated by a Common Language

• This was what John was thinking of—he recalled ones from his youth for decorating skin. These days, in both AmE and BrE, those are often called temporary tattoos. But decal in this sense is not limited to the skin ones. They might be images that are put onto, say, model airplanes, as in the top right photo here, from a how-to video.
  

3.  Images on vinyl (or similar material) that have sticky material on the image side, so that they can be stuck onto glass (or similar) and show through.  The companies I can find that sell them seem to call them reverse-cut vinyl [stickers/transfers/decals].

Image from diginate.com

 4.  Vinyl or other high-quality stickers of any sort, intended for use on glass, vehicles, etc.  I.e. not just the reverse-cut type, but anything of the type you'd stick onto a car window, say. 

• In this case, we can see a phenomenon called lexical blocking. Bumper stickers should be counted under this definition as decals, but since we have a special term for bumper stickers, i.e. (orig. & mainly AmE) bumper sticker, we don't tend to call them anything else. The vinyl stickers on cars that are called decals are different enough from typical bumper stickers (in size, shape, or placement) that they don't meet the criteria for that term.
  

In my idiolect, decal can be any one of types 2–4, but not the iron-on type. I would call those iron-ons or iron-on transfers. But when I looked up decal in dictionaries, I found the iron-on type potentially included in some definitions, like this one from Collins COBUILD, which gives transfer as the BrE equivalent.

Other dictionaries, like Merriam-Webster and Cambridge, limit decal to types of stickers and don't mention heat-transfer, so more like how I use it. 

But then I started asking my American friends—all from my generation, but different parts of the country—what they called the things they might iron onto a t-shirt, and one (she's originally from Kansas, but has more time in Wisconsin/Illinois) immediately offered decal. The others, generally from more eastern parts of the country, said iron-on or iron-on transfer or just transfer. 

And so I did a Twitter poll. The problem with polls is that you usually only want to hear from some people, but other people will want to do the poll. I don't know if those other poll-takers care that I throw away their data, but I do know that I have to give them the chance to give it to me because otherwise they pretend they're part of the target group and will thereby mess up my numbers. But after a bit of math(s), we can see (a) that Americans are fairly split on whether iron-ons are included under decal and (b) that my iron-on-excluding usage has slightly more users among my Twitter followers. Keep in mind that my followers may skew older (it's Twitter) and eastward (because of time zone issues).

This all provides more fuel for the idea that we shouldn't talk about what "the American" or "the British" term for something is. (Though I'm sure you'll catch me doing that sometimes.) There's a lot of variation in both, so it's better to think of most expressions as representing an American or a British way of saying things. 

Because of the limitations of Twitter polls, I could only ask about one facet of the word's potential meaning: whether or not iron-ons are included. Some followers responded with more specific meanings for decal than I have, for example, one said that he'd only use decal for type 2, in model-making.

For transfer, it's clearly an exaggeration to call it 'British-only' in all of the senses, since Americans do seem to use it for (at least) sense 1. Yet that's what some dictionaries do.

I am tempted to say that transfers have a reverse-print image that is pressed onto a surface, whether that be skin, fabric, glass, etc. (so uses 1-3 above). But there are enough companies out there selling non-reverse-print "vinyl transfers" that reverse-ness is not at this point a necessary condition for many people's understanding of transfer.

To sum up: 

• Decal is a fairly American word, but Americans vary in how they define/use it.
• Transfer as a noun for a type of image printing/attaching occurs in British English, but is also available in AmE, especially for the iron-on type.

PS: there is variation in how decal is pronounced in AmE, particularly which syllable gets the stress. You can hear more on YouGlish. In my experience, it's more common to put the stress on the first syllable. Thanks to Adonis in the comments for raising this.

walking verbs

footpaths/trails/ways

A path or track worn by the passage of persons travelling in a wild or uninhabited region; a beaten track, a rude path. (Chiefly U.S. and Canadian; also New Zealand and Australian.)

Related posts

birds of prey

buzzard and hawk

In the US, buzzard is another name for the turkey vulture (so-called because it looks a bit turkey-ish). In BrE it is for birds of the genus Buteo.

(BrE) buzzard

Turkey vulture/(AmE) buzzard

sea birds

skua / jaeger

AmE uses jaeger (from the German for 'hunter) for the smaller species of skua and BrE doesn't.  (Via Jim Martin)

Pomerine jaeger/skua

guillemot/murre

Another one from Jim. I'm going to let Wikipedia do the work for this one:

Guillemot is the common name for several species of seabird in the Alcidae or auk family (part of the order Charadriiformes). In British use, the term comprises two genera: Uria and Cepphus. In North America the Uria species are called "murres" and only the Cepphus species are called "guillemots".

Guillemot comes from the French name Guillaume (as we saw last time, naming birds after men is not uncommon).  Murre came from the UK, originally. It might be imitative, and might be related to Welsh morra or Cornish murr.

gulls

Jim Martin points out that mew gull (onomatopoetic for their call) is more used in AmE for the species called common gull in BrE, though these particular gulls are not all that common in UK. Wikipedia points out that there are broader and narrower meanings of mew gull, but I'll let them tell you about it.

Gulls in the UK are serious birds. The herring gulls common on much of the coastline are the size of ducks or geese. They are not shy about stealing food right out of your hands, which (given their size and stealth) can be very disconcerting. My worst herring gull memory (i.e. best herring gull story) was when we were at a park with our then-toddler and saw a herring gull with a pigeon halfway down its throat. Spouse chased it with an umbrella till it dropped the pigeon—the pigeon was too big for it to fly off with.

waterfowl

NAmE loon / BrE diver

goosander/merganser

(From Jim Martin). The common merganser is in BrE the goosander. Goosander has an obscure etymology. The first part is goose and the second part is probably from the Old Norse plural for 'duck'. (Merganser is the Latin name.)

Country(side) birds

lark

If I'd been smarter/cleverer, I'd have label(l)ed the last post "passerine (perching) birds" and not "garden birds", as that would've made for a clearer division between one bird-type and all others. But I didn't, and so I'm putting larks here, because they're more likely to be found on farms or mountains than in gardens. Anyhow, there is only one lark in North America, and Americans call it the horned lark, but the same species in Europe is called the shore lark. That particular species doesn't seem to extend to the UK, where there are other larks with their own not-needed-in-the-US names.

AmE horned lark elsewhere shore lark

observing birds

the hobby

Bird-watching is a term that seems more popular among people who don't do it as a hobby than people who do. The (more specialist—and often dismissive) BrE term for a bird-watcher who "collects" sightings of birds is twitcher (see comments for more info). Its use has spread beyond Britain, but is still heard a lot more in BrE, and it's more informal than "official". The OED's first example of it is from 1974, but they note a claim that it was coined in the 1950s and relates to the person twitching with excitement. The noun twitch thus came to be an expedition or gathering of bird-watchers. The intransitive verb twitch subsequently came to be used for serious bird-watching and a transitive version for spotting a rare bird. Here's an example of each (in that order) from the OED:

• 1977   New Society 17 Nov. 341/2   Those now in their thirties have been twitching for maybe 20 years.
• 2009   Birdwatch Winter 6/3   We can hope that in 20 years, birders won't feel compelled to charter flights to ‘twitch’ the lone, singing Canada Warbler.

Another term in the OED quotations is tick-hunter, which would mean you're searching for birds to 'tick' off your list, using the BrE sense of 'tick' (AmE 'checkmark'). These days, that sounds more like you're looking for small blood-sucking arachnids in the hope of preventing Lyme disease. There were no instances of it in the corpus I searched (see below).

In AmE, the specialist term has been birder, with bird becoming a related intransitive verb. OED's first citation for this is 1945. The word has spread beyond the US now.

In the GloWBE corpus, the clear winner for international word-of-choice is birder (the white here indicates it's not now especially AmE or BrE), and there are AmE/BrE differences in preferred hyphenation of bird(-)watcher, not necessarily in the order I might have predicted.

Green = more particular to that country. Pink = less

bands/rings

People who research birds often mark wild ones with a little thing{ie/y}* around a bird's leg. The thing{ie/y} is called a band in AmE and a ring in BrE. The verb goes the same way. In AmE the birds are banded and in BrE the are ringed. If you do that to a bird, you are a (AmE) bird-bander or (BrE) bird-ringer. For more, see Wikipedia.

* Sidenote: The OED tells me that thingy is 'originally and chiefly Scottish'. Thing(ie)s may have changed since that entry was updated in 2008—as the word seems widespread now. There is a spelling difference, though, in that Americans are more likely to style it as thingie.

birbs

And, denizens of the internet, I want to end with an important semantic question: When is a bird a birb?  The Audubon Society has been looking into it.