A plan to explore Venus using bird-like drones is one of the out-there futuristic mission concepts that NASA plans to study.
The BREEZE concept is one of seventeen visionary projects selected for further study. BREEZE has been selected for a Phase II grant, which will allow the researchers to continue studying the concept for another two years.
The idea for BREEZE is to use inflatable structures and inspiration from nature to build drone explorers. It makes a lot of sense because of the conditions on Venus. Venus has thick clouds that obscure views of the surface, so explorers need to get below the clouds to get a good view. Pressures on the surface are immense, as are the temperatures, so previous probes have only lasted a few minutes on the surface. The thick atmosphere is full of sulfuric acid clouds, so it is not a friendly environment, but it could be used for a craft that glides along the strong winds there.
Javid Bayandor explained in a statement that BREEZE will navigate the atmosphere at altitudes between 50-60 km and ride zonal winds to circumnavigate the planet every 3-6 days. Tracking weather patterns, determining atmospheric constituents, mapping Venusian magnetic field, and creating detailed surface scans are included in these studies.
You can see a full list of the concepts being studied on NASA's website.