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Unfortunately, my skills and understanding of radar and the like are very limited, but if somebody could enlighten me why there is no such thing as a dual bird/weather radar to switch to?
I've understood there there have been some (successful) attempts with ground station. It would add weight, but i'd guess that perhaps would be offset for some time by a single ruined engine.
There really is no such thing as "bird radar". Radar comes in a few frequency bands that have certain advantages depending on the distance, resolution and attenuation you need out of it. The band isn't the only factor here as the band will dictate what size dish you need and your aircraft nosecone will but a distinct upper limit on that. Weather radar is geared toward detecting rain drops and anything bigger than rain (hail, bugs, birds, etc) with reasonable distance and attenuation features (you want to penetrate into a storm). Birds will show up on this radar, though depending on smoothing and processing algorithms you may need a flock of them before they get drawn on the radar, at which point they'll look like some rain. A radar optimized to detect bird sized objects would probably use a wavelength that did not let you see things as small as rain drops and small hail.
Some other things to keep in mind are that the radar is not always on, and it should be off on the ground except during takeoff when needed. The reason for this is that you do not want to be putting radar energy into people, and they tend to be in the way on the ground. We only turned the radar on for takeoff when there was significant weather around the field and wanted to be prepared for requesting diversions. Aircraft radar tilt can also be adjusted, so we wouldn't be looking at birds in front of us, but clouds above and in front of us.
Wit that said, our SOP on fields with known heavy bird activity was to takeoff with the radar on and pointed forward because someone had the idea that the birds didn't like being in the radar beam. I have no sources to back that idea up, but it was written into our FOM.
Now assume you can takeoff and see a flock of birds on the radar. Do you have enough time to do anything about it? If so, what do you do, some maneuver away from them or do you turn into them in hops they take the evasive action?
In a real situation, what would a bird radar enable you to do with a positive detection with the time you have to react to it? Maybe throttle down the engines for a few seconds to avoid sucking in the birds.
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I don't know that a radar would provide enough of a warning anyway, if it could even see a single bird. And all it takes is one. The majority of birdstrikes happen near the ground, and the things I've seen have tended to be more to keep birds away from airplanes rather than trying to dodge them. They use cannons/noise-makers at many airfields and other means to keep birds away from low aircraft. And I've heard that the spiral painting on the compressor cones of many big jet engines, in addition to giving a visual indication that the engine is running, has a side benefit that, to a bird, it looks like the eyes of a predator and tends to scare the birds away from the engines. There have been mixed studies on the efficacy of that claim, but I don't know that any scientific research has been done to give a real yes or no. Boeing will claim that it doesn't matter. JAL claims that they had fewer birdstrikes on aircraft with painted spinners. I don't really know if it works or not.
In my experience, you aren't going to see-and-avoid most birds. You're simply moving too fast for either of you to get out of the way. I quit flying with only a few thousand hours, and I've hit several birds. And I don't know very many pilots who haven't either hit one or had a near miss. I've even been hit by a goose in my door when I while I was teaching in a 152, one of the few times that I can actually say the bird hit me and not the other way around.
The best way to keep from hitting birds is to try to avoid areas where birds are known to be flying, especially during migratory seasons. If you hear reports of a flock of birds at your airport, use a lot of caution. And report them if you see them. Try to minimize low flying. In most small craft, it's unavoidable. Your normal operating altitude is fairly low and right within the area that birds tend to fly. In bigger aircraft, try not to dally at lower altitudes, if you can help it. Climb to your altitude And if you're low to the ground (landing or taking off) don't put the aircraft in danger by trying to dodge birds. And every takeoff should include an idea of what you're going to do if you do hit birds.
From http://www.birdstrike.org/
"About 41% of reported strikes with civil aircraft in USA occur while the aircraft is on the ground during take-off or landing and about 75% of strikes occur at less than 500 feet above ground level (AGL). However, over 4,200 strikes involving civil aircraft at heights above 4,500 feet AGL were reported from 1990-2013 in the USA and over 430 of these were at more than 10,500 feet. The world height record for a bird strike is 37,000 feet (Griffon vulture off the coast of Africa)."
The weight of the bird radar would be trivial and it could easily fit in the nose cone; they aren't that big. They don't have to look nearly as far out as weather radar, All they have to do is indicate altitude and direction. Aircraft can easily avoid collision by changing altitude. They only have to miss the bird by being a few feet higher or lower, and birds oftentimes fly level at the same altitude, especially when migrating. The computer could be programmed to avoid collision by adjusting the angle of ascent or descent.
