Hackle can be pretty confusing. This FAQ is a work in progress, and I'll be adding to it over the next few weeks to hopefully provide some examples of different feathers and their uses.
First though, it might help to get a sense of where different feathers are located on a bird. Here's a rooster skin from Conranch. It is from a juvenile "genetic" rooster== a bird bred specifically for dry fly quality feathers as opposed to meat and/or eggs. I've used fly tying bobbins with different color thread to illustrate different areas of the bird. Normally for dry fly quality feathers however, you would generally not be buying a whole skin, but cape or saddle.
White spool bobbin points to the cape ( also called a "neck")
Gray spool bobbin points to the top of the cape. The top of the cape is where the feathers with the shortest barbs are found for the smallest size flies. Depending on the grade of the cape and the breeder, the smallest feathers will vary a bit, but generally on a $30 cape, you could reasonable expect to have size 18 or 20 and up. More expensive capes would tend to have even smaller feathers in this area of the cape. The size of the feathers are arranged in concentric rings around the skin on the cape. For example, if the tip of the gray spool bobbin points at a feather with barb length sized for 18 flies, feathers attached to the skin directly above it and below it would also be size 18. As you move down the cape (toward the left), the barb length of the feathers will get longer. At the bottom end of the cape you'd expect to find feathers for woolly buggers with longer softer barbs. The crescent shape on the far right is where the cape was cut from the head.
Yellow spool bobbin points to feathers that would be on the throat of the bird. These feathers are soft with long barbs and are not suitable for dry flies. Normally these would be trimmed from a cape and would not be included.
Black Spool bobbin points to the saddle. The saddle will have longer dry fly feathers (in total length) than the cape, but the barb length of the feathers on a saddle will typically come in a very limited range of sizes-- typically most of the feathers will fall within 2 or 3 sizes. Depending on the saddle, it might tie mostly 14 and 16 ( Whiting red label) or 10 and 12, or 12 and 14 dry fly saddles from most other breeders. If you tie flies in a limited range of sizes than a saddle may be the best bet. If you tie flies in a variety of sizes a cape or 1/2 cape might be a better bargain if you're just starting out.
The orange spool bobbin points to a "schlappen" feather found at the bottom of the saddle. This is a long webby feather with long barbs best suited to woolly buggers.
There's difference between "genetic" dry fly hackle bred specifically for tying dry flies and saddles and capes (also called necks) used for buggers that have "softer" barbs like hen necks and saddles and partridge feathers used on soft hackle flies.
The brown spool of thread sits on what would be the belly feathers of the rooster. These are also webby, soft feathers with long barbs not suitable for dry flies. Normally these would be trimmed from the saddle and not be included.
The easiest way to tell is to take a feather and bend the stem. A dry fly hackle will have stiff barbs that stick out straight and stick out individually. A saddle used on woolly buggers, and capes and saddles sold for streamers, hen cpaes and saddles etc will have "soft” feathers that tend to curve in the direction of the bent stem, and stick together ( these are said to be “webby”). There are likely to be some feathers at the very bottom of a dry fly cape that are a bit webby and would be better for stuff like buggers or streamer wings. The feathers at the bottom of the cape also tend to have the longest barbs. When you wrap a dry fly hackle the barbs should stick out straight from the hook shank, Bugger hackle and softer hackle like hen will tend to sweep back towards the bend. When you pluck a dry fly hackle feather, and bend it, you'll also see that the bottom of the feather will tend to have webby barbs, and at some point as you move up the feather the barbs will start to stick out straight. This is the portion of the feather used for dries. You can often tell the webby portion just by looking at the feather-- there should be a slight V coloration running along the stem, broader at the base of the feather, and quickly narrowing down where the dry fly quality part of the feather starts.
Good dry fly hackle tends to be expensive and can be either a neck (cape) or saddle. There are several differences between a dry fly quality neck and a saddle. The main differences come down to:
feather length (overall length of the whole feather). This relates to how many dry flies you can tie from a single feather.
and feather size (barb length, which is generally 1.5x the width of the hook gap for many dry flies).
To confuse things a bit, there are also different grades, and the quality (and price) from different breeders can vary quite a bit. Whiting uses Pro, Bronze, Silver, Gold and Platinum and has two distinct genetic lines of dry fly birds. Other breeders Metz, Collins Hackle, Conranch and house brands use grades 3, 2 and 1, with grade 3 being the least expensive.
Necks (capes) have a greater range of sizes (measured by barb length) so they'll tie a greater range of hook sizes. The overall length of the feathers is shorter than saddle feathers, so you'd typically get less flies out of a single feather. Grades of necks generally speak to the length and number of feathers, and the ability to tie smaller sizes. For example a Whiting Hebert Miner Pro Grade neck from Hook and Hackle might tie down to size 18, with a range of feathers for hook sizes 10 -18, enough to tie 350+ flies and run around 25 bucks. A Silver Grade Whiting neck might tie flies sized 10-26, and have more and longer feathers, enough to tie approximately 500 flies, but run considerably more at 90 bucks. In this case, you'd be paying not only for greater quantity of flies, but the real premium is for the ability to tie 20, 22, 24 and 26 sized flies. Feathers on a cape tend to be smallest in overall length and in barb length at the top of the neck where there’s a V cut, and will gradually run longer in overall and barb length as you move down the neck. If for example you pull a feather with size 16 barbs on the right side of the neck, the same area on the neck on the other side is likely to have 16 sized feathers too, since the feathers sizes run in rings as you move down the neck from smallest to largest. Feathers at the bottom of the neck may not be dry fly quality, and might be better used as bugger hackle or as wings in feather winged streamers. Typically dry fly sizes are in the top 1/3 of the neck.
Saddles tend to have longer length feathers and are very easy to work with since they tend to have thinner more flexible stems. Because of the length of the feather it’s not uncommon to get 6-7 flies out of a single feather, and the feather’s barbs will run true to size the length of the feather. But where capes (necks) have a wide range of sizes, saddles tend to be strongest in 2 sizes, with realtively few feathers larger and smaller than the bulk of the feathers. Whiting saddles tend to run strongest in size 14 and 16 with a few size 12 and 18 feathers. Saddles from other breeders may run a bit larger with mostly size 10-12 or 12-14. In the case of saddles, the different grades refer to the length and quantity of feathers, so that a bronze whiting saddle might tie 500 flies in mostly size 14-16 and run 55 bucks or so, and a silver grade Whiting saddle might tie 900 flies in the same size range as the bronze, and run 75 bucks. Dry fly saddles are a good choice if you tie in a limited range of sizes, as long as you make sure the individual saddle is strong in those sizes. If you’re ordering sight unseen from a fly shop have them pull it and check. Another thing to be aware of is that the genes that control the development of feathers in the cape are separate from the genes that control the quality of the feathers in the saddle, and that typically it takes longer for saddle feathers to mature. Some breeders raise their birds specifically for their capes and harvest the bird when the cape is ready- and the saddle feathers can be a bit soft. Other things that affect the quality of dry fly hackle are twisted, thick or oddly shaped stems that make wrapping difficult, and the barb density (number per inch of stem). Colors also vary by breeder, with some lines strong in natural dun shades, barring and one off variants like Whiting's Hebert Miner line (green label) and Collins Hackle, and some use dyes for their duns to achieve consistency (whiting red label)
Whiting is widely considered to have the best quality dry fly hackle in both capes and saddles--- but it’s expensive. Another thing to keep in mind with Whiting is that there are 2 lines of dry fly hackle. Whiting Red label (their oldest and most advanced. Typically when people talk about Whiting dry fly hackle, this is what they're referring to). These are packaged with a Red label. They also now own a line of called “Hebert Miner” which comes from a different genetic stock and has a Green label. The Hebert Miner line has very rich colors and the quality of these capes and saddles will most likely greatly improve with Whitings intensive breeding expertise. Right now a comparable grade Hebert Miner Cape will not tie as small a fly (by a hook size or two) as a comparable grade Red label. They are rich in color, and the Pro Grade Hebert Miner Capes at 25 bucks from Hook and Hackle are an excellent value, (elsewhere they run 30 bucks) and will typically tie dries sizes 10-18, with some capes tying down to size 20. Ron at Hook and Hackle is a pleasure to deal with, and I'm sure you got a good value for your dollar if you bought their house brand.
I’ve attached a couple of shots of a dry fly quality neck and saddle. A Whiting Hebert Miner Pro Grade Natural Medium Dun (note the Green label) in pic 1, a Whiting Silver Grade Dyed Dark Dun Saddle (note the red label) in pic 2, and a pic of two size 16 feathers, one from the cape, and one from the saddle. The feather from the cape will tie 2-3 flies, and the feather from the saddle will tie 6-7 flies, all size 16. Also in the 3rd pic is a a Griffin Hook and Hackle Gauge. These run 3.50 to 5 bucks and fit on the stem of your vise. You bend the feather around a pin on the gauge and can quickly size feathers by seeing where the barbs fall against the concentric rings. You can also use it to size hooks by comparing the gap to the chart on it. It's pretty handy if you're just starting out-- after a while you'll be able to just wing it by eyeballing, but for now, it might help you get better proportions. In the meantime, you can bend the feather around the shank of a hook (held in your vise) and see where the barbs fall- they should be about 1.5x the length of the hook gap for most Catskill style flies. And again, the feather barb length will run shortest at the top of the neck and get longer as you move down. Typical dry fly sizes 12 and smaller in the top 1/3 of the neck.
I hope this helps a bit. Keep asking questions if you have them.
Comparing Neck with Saddle Feathers