Why are bird strikes on approach or landing not as common as on takeoff?
I've heard about lots of bird strike incidents that occured during a takeoff roll or the early phase of takeoff climb but hardly heard of bird strikes on approach or landing.

This is always a dangerous thing. Only because you hear more bird strikes that occur on takeoff, it does not mean there are more at takeoff.
I found, for example, this report about bird strikes from the year 2000. It says:

[...] 38% of the bird strikes occurred during take-off
and climb, and 56% during approach [...]

That means there are more bird strikes during approach than on takeoff. I assume things haven't changed a lot since then.
This question is even answered in the Wildlife FAQ Section of the FAA:

Q: Do most bird strikes occur while in flight, at takeoff, or landing?
A: About 60% of bird strikes with civil aircraft occur during landing phases of flight (descent, approach and landing roll); 37% occur during take-off run and climb; and the remainder occur during the en-route phase.

A more specific statistic:

Source

Possible reason for subjective perception of bird-strikes happening more often during departure
I thought a little about it and came to following possible reason: After a bird-strike on final, the pilots will continue landing. It would be unwise not to land immediately. For the passengers it will look like a normal landing. If the bird damages the engine, there is only a small change of sound, because the engines are running very low.
However, when a bird-strike occurs while taking off, there is immediate action taken by the pilots. And because the engines are at or near full thrust, the sound of a dying engine can be perceived by the passengers. Last but not least, a departing aircraft has a much higher speed than a landing one, which means more damage.
So, for newspapers, a bird-strike at take-off is more dramatic and drama sells.

More damage to the plane than a bird-strike on final
Passengers not reaching their destination
Dramatic passenger interviews about their &quot;near-death-experience&quot;

A newspaper is not interested in a bird-strike on final, where everything went fine and no passenger noticed anything.
To support my theorem, I googled &quot;bird strike&quot; and clicked on the &quot;News&quot;-tab. I looked through every article that had to do something with an bird-strike incident. 5 out of 6 articles were about a bird-strike on take-off. That's over 80%.