Indigo Buntings are small migratory songbirds that breed across most of the eastern and central United States and southeastern Canada during the summer. They migrate south to spend the winter in Florida, Mexico, Central America, and the Caribbean islands. Their annual migrations can cover thousands of miles, requiring remarkable navigational abilities to travel between their breeding and wintering grounds each year.
Do Indigo Buntings use stars for navigation during migration?
Yes, research has shown that Indigo Buntings use stars to help guide their navigation during migration. They are able to determine their latitude and longitude by observing the positions of stars in the night sky. This ability to use celestial cues for orientation is called “true navigation.”
Studies where buntings were captured and released under an artificial starry sky showed that they recalibrated their sense of direction based on the artificial star patterns, confirming their use of stars for navigational map reading. Even on overcast nights when stars are obscured, buntings are able to recalibrate their position using their internal memory of star patterns.
How do Indigo Buntings determine direction and location from stars?
Indigo Buntings are able to determine both direction and location by observing three main elements of the night sky:
- The north star – Polaris remains fixed, allowing the birds to determine their north-south orientation.
- The rotation of constellations around the pole star – this allows them to determine their east-west direction.
- The height of stars above the horizon – this provides latitude information as star height corresponds to latitude.
By combining these celestial cues, the buntings create a map-like representation internally that allows them to determine their geographic location and orient themselves in the proper direction during migration.
What brain regions are involved in processing celestial information?
Research has identified two brain regions that play an important role in processing celestial information for navigation in migratory songbirds:
- The supra-mamillary nucleus (SuM) – involved in determining direction by reading the night sky.
- The hippocampus – encodes information on star positions and celestial rotation patterns to create an internal map.
Lesioning studies where these brain regions were damaged showed that birds could no longer orient properly using celestial cues.
How does weather impact Indigo Buntings’ ability to navigate using the stars?
Inclement weather such as heavy cloud cover that obscures the night sky can impact Indigo Buntings’ ability to effectively navigate using celestial cues. However, studies show buntings have adaptive strategies to cope with these challenges:
- They have an internal magnetic compass as a backup for orientation on overcast nights. This isn’t as precise as celestial navigation but provides directionality.
- They likely have a mental “map” based on memorized star patterns that persists even when stars are temporarily obscured.
- They have the ability to recalibrate their position and bearings when the stars become visible again after a period of obscuration.
So while heavy cloud cover makes celestial navigation more difficult, Indigo Buntings have redundant mechanisms and cognitive capabilities that allow them to successfully compensate.
Do Indigo Buntings also use other cues to navigate besides the stars?
Yes, in addition to using stars, Indigo Buntings also rely on these other cues to help guide their long migrations:
- The earth’s magnetic field – they have an internal magnetic compass that provides directional information.
- Visual landmarks – they use distinct landscape features like coastlines, mountains, rivers, etc. to orient themselves.
- Olfactory cues – smells may activate innate directional tendencies or help locate breeding/wintering sites.
- Sun position – provides directional information during the day.
Indigo Buntings integrate all of these different sensory cues seamlessly to find their way between their summer and winter sites. The starry sky provides critical map and compass information at night when other cues are unavailable.
Do young Indigo Buntings know how to use celestial navigation immediately?
No, the ability to use the night sky for navigation develops over the bunting’s first few migrations. Young buntings on their first migration rely more strongly on the earth’s magnetic field and learned landmarks. Celestial navigation strategies take longer to master:
- Young buntings first migrate in the company of experienced adults that help guide the route.
- The neurocircuits involved in processing celestial information take time to fully develop.
- With each subsequent migration, their celestial navigation improves and becomes more precise.
- By their second year, they have developed full navigational map reading abilities.
So this advanced skill is slowly honed over the initial migratory journeys of a bunting’s life.
How early in life does navigation ability start to develop?
Indigo Buntings start developing basic components of their navigation ability at a very early age while still in the nest:
- Within days of hatching, they already demonstrate magnetic compass orientation in lab experiments.
- Brain regions involved in spatial mapping and orientation start developing in the nestling phase.
- They start making short orientation flights while still being fed by parents, allowing them to learn landmarks.
- Migration onset is triggered by genetic and hormonal changes later in the summer.
So even before they can fly independently, Indigo Buntings already have some early navigation abilities developing that will be critical for their first migration.
How does artificial light pollution affect Indigo Buntings’ ability to navigate using the stars?
Increasing artificial light pollution, especially bright lights pointing up into the night sky, can interfere with Indigo Buntings’ ability to view and use the stars for navigation. Effects of light pollution include:
- Disorientation from bright lights that obscure star visibility.
- Altered directional tendencies when migrating through large brightly lit cities.
- Disruption of celestial compass calibration if star patterns are obscured.
- Interference with development of celestial navigation abilities in juveniles.
Buntings migrating through urban areas with bright night lighting often become disoriented and collide with buildings or communication towers. Minimizing light pointing skyward in urban areas may help reduce impacts to migratory songbirds.
Conclusion
In summary, Indigo Buntings are amazing celestial navigators that use information from the night sky including star positions, constellation rotation, and star height to determine their latitude, longitude, and direction during migration. This advanced skillset allows them to undertake long-distance migrations spanning thousands of miles to move between their breeding and wintering grounds. While celestial cues play a critical role, buntings also integrate other sensory information like the magnetic field lines, landmarks, and sun position to successfully find their way on these epic journeys.
