The ones in Canada are ridiculous. They are extensions of the forests with tall trees and under growth where the animals are never able to see the roadway beneath. I can't imagine what those must have cost. In the national forest they are ~ 5 miles.

What kind of wildlife migration occurs in Texas besides birds?

Animals cross highways

Bucks can roam up to 7 miles from their home territories during rut and some have moved farther. There is seasonal movement of all kinds of wildlife depending on habitat conditions and food and water.

Some areas show patterns of higher rates of collisions by cars with wildlife. So these can improve road safety for car passengers as well.

TxDOT spends billions every year and helping wildlife is helping pass our heritage onto future generations.

President Teddy Roosevelt, a Republican, offered this thought:

“Defenders of the short-sighted men who in their greed and selfishness will, if permitted, rob our country of half its charm by their reckless extermination of all useful and beautiful wild things sometimes seek to champion them by saying the ‘the game belongs to the people.’ So it does; and not merely to the people now alive, but to the unborn people.

“The ‘greatest good for the greatest number’ applies to the number within the womb of time, compared to which those now alive form but an insignificant fraction. Our duty to the whole, including the unborn generations, bids us restrain an unprincipled present-day minority from wasting the heritage of these unborn generations. The movement for the conservation of wild life and the larger movement for the conservation of all our natural resources are essentially democratic in spirit, purpose, and method.”

Look up the amount insurance companies payout each year to people who have hit deer. Keep in mind that number doesn’t include the motorists who don’t have insurance or only have liability insurance. Also, keep in mind people do die in some of these accidents. I know the overpasses are expensive but the animals do use them when they are placed in the right place.

Well obviously animals cross highways. They will keep crossing highways. Unless you put it in the path of a migration route... what migration in Texas? What is the range of a whitetail?

Here is a statement from WG&F about the cost of wildlife collisions. If it's yhid high in Wyoming with our small population I can only imagine how much cost is involved with collisions nearer large cities or urban areas.
They put up high fences along the highways to direct wildlife towards the crossings, that fencing can not be cheap either but we have in areas without crossings too.

Safer Roads For Wildlife And People
Annually, there are an average of 6,000 vehicle collisions with big game in Wyoming, resulting in $20-23 million in wildlife costs and $24-29 million in personal injury costs. Game and Fish, as well as the Wyoming Department of Transportation and various wildlife and community groups, want to reduce those numbers by taking action to give wildlife the green light for safe passage.

Check this webcam out for one of Wyoming overpasses: http://www.trapperspoint.com/

We have them all over out here in the West. Both over passes, and underpasses. Here they high fence the area on both sides, and funnel them thru when migrating back and forth. Benefits the migration, and eliminates a lot of vehicle collisions/deaths. Since a lot of our speed limits are 65-80 mph, you really don't want to be hitting an elk or moose!!!

I had read how great Banff ecologically was until I saw first hand dead old growth fire suppressed forests. Such a joke

They they their place, but there are no great migrations in Texas

There is no migration of wildlife to speak of in Texas that I am aware of that could justify this expense.

I would ask then how many vehicle collisions happen in that area, must be quite a few if they need help with crossings.
Don't get caught up on the migration reasoning, just having large numbers of deer crossing the road and causing accidents is good enough argument behind one.

It is just about in the middle of San Antonio...1.487 million people (2018).

Then let the insurance companies pay for it. Their willingness to pay is a pretty good indicator of how bad we need it, IMO.

There are wildlife bridges on the Arizona side at Hoover Dam, about 20-30 miles through the mountains are high fenced to keep the Bighorn Sheep off the road.
One reason they are expensive, game warden said, is they are built the same as a vehicle bridge so trucks doing maintenance can drive on them.

I have seen deer on the bridge,
Location of a bridge, (35.8882094, -114.6210034)

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Until I retired in 2017, I drove 100 miles a day round trip on Interstate 80 right along the Platte River. Wasn’t unusual at all to see whitetail crossing over the interstate on the gravel roadoverpasses during early morning and evenings. Had nothing to do with migrations. Just normal feeding patterns and the rut. Would really help if they were on a migration route but we have none. Those overpasses didn’t cost $23M and their purpose was for vehicles. The benefit to the deer was just a freebie.