I'm going to be quoting some from this link:
You said: "1) Some birds have longer beaks than others.
Some birds might also develop a strange tendency to jerk forward. In fact, many such nervous system quirks could have been coded in the DNA, but most of them would not help a bird, and those birds would be unlikely to live to reproduce in the natural world. There is no selection involved...only lack of advantage.
We saw in the previous post that this rise of new traits, including nervous system quirks and
longer beaks, could occur
with a chance mutation, a change, in the DNA code which is conveyed to a new individual in the sperm and egg of the parent birds.
food supply in trees ran low, there would be an advantage for tree-feeding birds who could dig DEEPER into the bark to get burrowing insects and other bugs. More of the deeper digging ones might live to procreate one or more years than birds who experienced famine in bad periods because of a shortage of bug food.
Over a thousand generations, this could mean the birds with stronger neck muscles and longer beaks would become more numerous than the first wave of them that appeared."
I can't help but point out (correct me if I misunderstood this) that this theory rest on a bird that has nervous system quirk and a long beak being born while the food supply was low. Then you say that bird would have a natural advantage because it could dig further into a tree for food.
First of all it takes an amazing anantomy to pound a tree for bugs. From that link up top,
"For starters, the Creator has greatly reinforced the woodpecker’s skull with bone. This is necessary if the head is not going to break into pieces. He has given the woodpecker a stronger bill than most birds. It must be strong enough to dig into a tree without folding up like an accordion. The bill is chisel-tipped, and when the woodpecker is chiselling away there is a lot of sawdust. Normally in birds, the sawdust would enter the nostrils, but the woodpecker has been designed with slit-like nostrils covered by fine wiry feathers to prevent the sawdust from entering.
Also, the beak and brain itself have been cushioned against impact. In most birds, the bones of the beak are joined to the bones of the cranium—the part of the skull that surrounds the brain. But in the woodpecker the cranium and beak are separated by a sponge-like tissue that takes the shock each time the bird strikes its beak against a tree. The woodpecker’s shock-absorber is so good that scientists say it is far better than any that humans have invented.
For added protection to its brain, the woodpecker has special muscles which pull its brain-case away from its beak every time it strikes a blow. But this is only part of the story. If the woodpecker’s head were to twist even slightly while hammering the tree, the rotation of its head, combined with the force of pecking, would tear away the bird’s brain. But God, the ultimate Designer, has created the woodpecker with superbly co-ordinated neck muscles to keep its head perfectly straight. Thus the bird can withstand the enormous shock it inflicts on itself year in, year out, many thousands of times a day.
Added to the uniquely designed neck muscles, shock-absorbers, head, and the other amazing aspects of the woodpecker, there is the unique tongue. The typical woodpecker, after flaking off bark and drilling a hole in wood to expose insect tunnels, uses its long tongue to reach deep into the tree to retrieve insects and larvae. Without the long tongue, there is no way the woodpecker could retrieve the insects.
To help capture the insects, the long tongue has been specially designed with glands that secrete a sticky substance. The insects and worms stick to this long tongue like flies to fly-paper.
How does the woodpecker know it has caught the insects? The Creator has given it a tongue with a hard spearhead with bristles pointing rearward, which is attached by tiny fibres of the protein collagen. As the tongue probes a tunnel, the impact of the spearhead on any object jams the head back along the shaft. Nerve endings are precisely located in the fluid-filled spaces between the collagen fibres. They provide the brain with information about the type of material contacted; thus, the woodpecker knows whether it has secured an insect or hit the hard wood of a tree. Once the insects stick to its tongue, the woodpecker pulls them from the tree, then pulls in its long tongue and scrapes the insects off into its mouth.
Where does the woodpecker hold such a long tongue when it is not in use? It cannot just roll it up and store it in its beak, for there isn't room. The Creator has provided a unique solution to this problem. The tongue of an ordinary bird is anchored in the back of its beak, but this will not work for the woodpecker, because its tongue is too long. Therefore, the tongue of the woodpecker is anchored in the right nostril. After it emerges from the right nostril, it splits into two halves. Each half passes over one side of the skull underneath the skin, comes around and up underneath the beak, and enters through a hole in the beak. Here the two halves combine. Thus, when the woodpecker is not using his long tongue, he rolls it up and stores it in the right nostril."
All these things must be in place at once for a woodpecker to get a meal. Whatever bird (with a nervous system problem) you think started digging into a tree could not have done that without an amazing anatomy. And if it could, then why would it need to evolve such complacated systems?
Here is some more from that link:
"First, how could the woodpecker have evolved its special shock-absorbers? If it had started without them, then all the woodpeckers that were alive would have beaten out their brains long ago. Therefore, there should be no woodpeckers left. And if there had ever been a time when woodpeckers did not drill holes in trees they would not have needed the shock-absorbers anyway."
"Second, how could the unique arrangement for the woodpecker’s tongue have evolved, if, in the beginning, its tongue was anchored in the back of the beak, as it is in ordinary birds? How did the tongue manage to move into the right nostril? If the anchor suddenly hopped from the back of the beak up into the right nostril, the tongue would be too short. And during all the intermediate stages, would the tongue have been long enough to reach the insects and worms inside a tree so the woodpecker could eat and survive?"
The woodpecker couldn't have evolved slowly. It would have had to come toghether all at once to survive.