ornecology

The majority of hummingbirds have what we call a complete preformative molt, this means they replace all their juvenile feathers shortly after leaving the nest. So younger birds can look identical to older birds. So we can’t age hummingbirds how we age other birds, with molt limits or retained juvenile feathers. Instead we look at their bills. Young hummingbirds have bill striations or corrugations. These are small grooves running along the length of the bill. When young hummingbirds leave the nest their bills have these corrugations running down 100% of the length of the bill. Over time, these striations fade away as the bird gets older. It’s hypothesized these little grooves function to help support the bill as baby hummingbirds usually have softer bills when leaving the nest. As the bill keratinizes and hardens, it also smooths out. A study from the Institute of Bird Populations showed that Anna’s and Rufous Hummingbirds will take about 6-8 months to lose these corrugations, though many adult birds will maintain about 5-10% of the bill with striations for several years. This amount of time to lose striations isn’t well documented in tropical hummingbirds, and likely occurs quicker over a 3-6 month period. With a hummingbird in the hand, we can look at the percentage of the bill with these striations. Birds with more than 10% of the bill corrugated are younger birds in their first cycle or first year. Birds with 10% or less striations are unknown or what we call M-FCF (minimum first cycle formative). This means we can’t rule out this isn’t a younger bird, since they lose their bill striations before they start their second year or second prebasic molt. Here we see both bill corrugations and the bird is molting out of juvenile plumage. Lately we’ve been catching quite a few young hummingbirds, showing us we have some happy breeding birds around. **All birds handled with proper permits by trained ornithologists**