As we walked some of the trails we heard the harsh calls of Steller’s Jays and got our best looks yet of the trip! Then, as we were leaving we saw what we’re identifying from its display as a rufous hummingbird; it was not a lifer for either of us but cool to see again out west. It did a giant loop in flight and would pause at the top. Eventually, it was chased off by another hummingbird.
At Luther Burbank Park we saw our lifer bushtits.
At Lake Sammamish State Park, I saw my lifer mink!
Though the following terms aren’t all the same, they describe whether or not breeding birds occupy the same territories as they did in the previous year.
- breeding dispersal – this is a commonly used term, especially in ornithology
- migratory nomadism – comes up in grassland bird literature
- fidelity – more broadly used in ecology
- return rate – a phrase used with other meanings in other disciplines, but also used in ecology
- philopatry – can add “breeding” before it to specify
So, in my case, to find as much information as I can whether grassland birds return to the same place or not in subsequent years (and why/when/what modulates it), I’d need to search through all these terms. The 1st 2 are my favorites because of their prevalence within my sub-disciplines, and are what I’d use in my own papers to increase the chances my target audience will find my paper in a search.
My to-date only 1st authored paper starts to explore this phenomenon, and it’s a running theme throughout my dissertation. What do we know about breeding dispersal, and how do we know? One of the most common and rigorous methods is to look at return rates of banded, marked or otherwise identifiable individuals.
- return/recovery of a banded individual: ideal! We know exactly “who” that individual is, where we caught it, how old it is/was, gender, etc.
- failure of a banded individual to return: we don’t know what happened to it. It could have died or gone elsewhere
We can map territories, but without being able to identify who’s holding it, we don’t necessarily know when a territory is taken over nor by whom. I read an interesting paper (Siegel et al. 2015) that used age classes to determine whether dispersal of juvenile or adult birds was the predominant vector of colonization for a disturbance-dependent species. At a coarser scale, we can look at how occupancy of areas changes year-to-year; in other words, we can see if as many individuals of a species return to an area as the previous year. Scaling up that concept, we can look at distributions with broad-scale data sets and how distributions of individuals change between years (which is the scale at which I’ve gotten involved with my research :)).