As the birds’ profile matched that of Unmanned Aerial Vehicles (UAV), Air Force jets persisted with the recci, including surveillance of the local airspace in the area.

Security concerns of the Indian Air Force across the Pakistan border met an unexpected but not-so-pleasant surprise this year. After radar signals indicated that unmanned aircraft were heading toward the Indian territory, the Air Force carried out sorties along the Gujarat border for several weeks this year. 

But the sorties proved futile as the signal would disappear after fighter jets from Jamnagar  would take off, only to reappear once the jets left the area, reported The Sunday Express.

Aug 2013:Army reports UFO sightings in Ladakh, again 

After this aerial exercise continued for weeks, IAF flight controllers finally traced the intruders: Large flocks of migratory birds heading for water bodies in Gujarat, flying at high speeds with the help of strong tail winds.

The force, however, was not clear about the species of migratory birds.

A report on the incidents reveals that between December’12 and February’13, radars placed them as “slow-moving tracks of variable heights of 4 to 6 km and variable speed from 100 to 250 kmph”.

As the birds’ profile matched that of Unmanned Aerial Vehicles (UAV), Air Force jets persisted with the recci, including surveillance of the local airspace in the area, the report says.  

The source of signals was traced to birds when the Air Force contacted the Nalsarovar and Thol bird sanctuaries and authorities said the possible route and flight profile of the tracks matched those of birds migrating to Gujarat.

UFO or Chinese lanterns? ISRO team to visit Leh to solve mystery of flying objects

Now, the IAF will trace migratory patterns and the months in which birds cross over from across the border, the reports adds.