Manfrotto 3011 tripod legs and 3029 Pan/Tilt head are both rated to support 13.2 lbs.

The tripod and head together probably weigh just over 7 lbs (4.8 lbs for the leg set, 2.3 lbs for the head).

Both are discontinued models, so these specs are from various sources online.

The problem is that aluminum does a poor job dampening vibrations. Carbon fiber would have a better weight/capacity ratio and absorbs vibrations better. Plus, matters are made worse, there is less stability if you have to raise the tripod center column at all to have your camera at adequate height. Three-section legs are good, the fewer the better for stability although this limits how small the tripod can fold for storage and carrying. For a field tripod I'm not a fan of thumbscrew or flip-lever leg locks, either, because they can catch on cuffs, sleeves and branches. I prefer twist-type leg locks, such as Gitzo uses.

The 3029 head is pan-tilt type that's pretty large and has protruding handles to catch on things while being carried. I would not recommend a fluid head either, primarily due to the weight, but most also have protruding handles, and many cannot be "tilted up" for portrait orientation of the camera (That's okay when using a lens with a tripod ring... But what about the times when you don't?).

Those tripod head types are workable, but many wildlife/bird shooters use a more compact ballhead or, especially with long telephotos like your 150-600mm, a gimbal head.

Unfortunately, you really have nowhere near enough budget to get a significantly better tripod and head. Taking the above into consideration, one of the least expensive leg sets available meeting all these criteria is the Feisol 3301... carbon fiber, 3-section legs, no center column, yet 55" tall (legs alone), twist (Gitzo) type leg locks. This tripod weighs 2.6 lbs. and is rated to support up to 19 lbs. This tripod leg set sells for $280.

Induro CT113 is similar, except it uses a center column to reach 59" and costs a little more: $325.

From there on, prices go up and up. And this is just for the leg set.... no head or other accessories.

One of the least expensive, yet heavy duty ballheads is the Smith-Victor BH8. It costs $60, weighs 1.6 lbs and is rated to support up to 40 lbs. It also has an Arca-Swiss type quick release platform (which may be necessary, see below). I have a BH8 on one of my tripods and it's surprisingly similar to a $385 Kirk BH-1 that I have on another. Only time will tell if the rather new BH8 holds is durable as the 15 year old BH-1 has proved to be (I doubt it, but hey, $60).

Two minor "issues" with the BH8 ballhead: When it first arrived the panning movement was very stiff. I took it apart, cleaned out the heavy grease they had used to lube the ball bearings, and replaced it with heavy oil (bicycle chain oil). Fairly simple fix, actually... just a few screws in the bottom of the head and some caution to not lose any of the small parts, put it back together correctly. Also, the BH8's quick release platform has a safety lock button that only works properly with their own quick release plates (one small one is provided with the head). That safety lock gets in the way of using other and longer A-S type lens and camera plates... it simply unscrews to allow others to fit.

The Arca-Swiss type quick release system is the most universal... many manufacturers offer products that use it. And it's necessary for gimbal type heads, in particular, to allow camera and lens to be adjusted for balance. To use it, though, you'll also need to buy a special camera plate as well as lens plates for each of your lenses that have a tripod mounting ring. A proper anti-twist camera plate will cost around $50 to $60, and lens plates cost between $25 and $65 depending upon size and quality.

Now, for use with your big Tamron lens, you will likely find a gimbal most helpful. This type of head can be tightened up for max steadiness... Or, often is used "loose" with moving subjects, to allow for smooth panning and tilting while tracking your target.

There are two types of gimbal heads. One I call a "full size" head, for lack of a better term. The other is "Sidekick" type, after the one sold by Wimberley (who sort of invented gimbal heads). A full size gimbal is needed for the heaviest lens/camera combos, replaces the ballhead completely and makes the tripod pretty much "large lens only" until the heads are swapped back. The "Sidekick" type is for use with slightly lighter rigs, costs less and is used in conjunction with the ballhead.

For example, this is a full size gimbal:

http://tripodhead.com/products/wimberley-main.cfm

And this is the Sidekick:

http://tripodhead.com/products/sidekick-main.cfm

Full size gimbal heads are made by many manufacturers and most weight close to 3 lbs. Prices range from around $100 for cheap Chinese-made knockoffs, to $500 or more for the very best. MTShooter, here on UHH, is the N. American dealer for Nest gimbal heads that sell for about $300 are the only ones I'm aware of made of carbon fiber to save a bit of weight and better absorb vibrations. Wimberley, Jobu, Kirk, RRS, Induro, etc. are all aluminum, AFAIK. This full size type head is recommended for the very largest and heaviest telephoto lenses, such as 600/4, 400/2.8.

I'm aware of only two of the smaller "Sidekick type" gimbals... The SK-100 Sidekick from Wimberley themselves ($250) and an Induro GHBA ($200). Both these are aluminum and weigh about 1.5 lbs. The ballhead stays in place and this type gimbal simply slips the head's Arca-Swiss type quick release platform. These are capable of supporting up to 500/4 lens (around 8 lbs or more, lens alone), so would easily handle your Tamron 150-600mm.

There isn't much difference in weight between the full-size gimbal mount (about 3 lbs.) and the combo of a fairly heavy duty ballhead and a "Sidekick" type gimbal (roughly 1.5 lbs each). The main difference is load capacity (full size is better for the biggest lenses) and ease of the Sidekick type switching your tripod rig back and forth between standard use and long-lens gimbal use.

With any of these gimbals, a long lens plate makes it possible to move the lens/camera combo back and forth a little to achieve good balance, which allows moving the entire assembly smoothly with a light touch, to follow moving subjects. Great for sports, birds and other wildlife.

So, all in I figure a very minimum:

Feisol 3301 leg set: $280
Smith-Victor BH8 ballhead: $60
Induro GHBA gimbal: $200
Lens plate (Desmond DPL-100): $17
Camera plate (Acratech for D7100): $40

That's almost $600 and is "bare minimum".

Other valuable accessories:

LegCoat covers for tripod legs, that make them more comfortable to carry, as well as protect the carbon fiber from possible damage: $50

Leveling platform that goes between head and legs, makes for faster setup and is especially helpful when using gimbal heads. Manfrotto 438 for $90 is a reasonably priced, universal type (Gitzo's are faster and easier to use, but are not universal and cost considerably more... $250+). A leveler adds a 1.5 lbs to the tripod rig, but I consider it worthwhile.

Tripod carrying/storage bag: about $50.

Personally I haven't used the above tripod leg sets, so do some more research on them before buying. The Feisol 3301 may not be sturdy enough.

I use several Gitzo "3-Series" Systematic carbon fiber tripods.... two older model G1325 Mk II and one G1348 Mk II. These are rated for 35 lbs. or approx. twice the capacity of the leg sets mentioned above, but they also are larger and weigh more (probably about the same weight as your 3011 leg set). Not long ago I bought a couple of them used for $325 and $400 respectively, both in top shape, with some accessories and including shipping (For comparison, current versions sell new for $900 to $1000 for the leg set alone... Plus each of these used ones happened to come with accessories I wanted, that normally sell for another $250-$295 new.)

I use two fairly heavy duty ballheads... a Kirk BH-1 I've had for many years, and the Smith-Victor BH8 I mentioned above. I also use a Wimberley Sidekick (along with those ballheads), as well as one of the cheap, Chinese knockoff full size gimbals (that makes me a little nervous with some of my bigger lenses... I may replace it with a Nest eventually).

An alternative is a monopod... Lighter and simpler to use, as well as lower cost. It might even double as a walking stick, when hiking. But of course it isn't fully self-supporting like a tripod.

Hopefully this helps you shop around. I'd recommend spending more money to get a better tripod, that you'll be more likely to enjoy using and less likely to find inadequate and need to replace in a year or two. Bought right, a tripod can almost be a once-in-a-lifetime purchase (one I have is 30+ years old and another that I still use I bought 15 years ago).

I've been viewing Regis's posts and have picked up some settings from him for shooting birds. However, your bird perched setting is a new one for me to put into my book. Thanks so much for that tip.
I agree that purchasing a good tripod and head is much better than throwing good money after bad.
My problem is that I've only been shooting birds in flight since late last summer. My knowledge of good vs bad is extremely minimal. So much so, that even knowledge of the different heads and what they achieve is a bit confusing for me.
So, I'm faced with counting on information I obtain from you experienced hoggers and the internet.
Thus my reason for this thread.
To actually handle and test different tripods and heads is not a possibility for me. There is only one camera store within 100 miles of me and that is a Best Buy Store. For which I am not thrilled. Understandably, big box stores have big overhead, and limited variety thus inflated prices IMHO.
Therefore, I very much value the information I've obtained in this thread and will do my best to increase my budgetary constraints.
I'm very motivated to learn from you experienced birders, and have to say there is absolutely nothing more thrilling for me than finding and photographing big majestic birds. I think I'm worse than a kid in a candy store when I've found a large bird to photograph. The excitement simply overwhelms me.