I am wondering what makes these birds choose a particular tree or trees to roost in. I could hear them in the evening, their loud racket, but it took me a while to find them, they are a few blocks away from me. Now I can watch them roosting. They are very big eucalypts, with no fruit or flowers
so I am wondering what made them choose these trees out of all of them around here.
Elizabeth
"Rainbow lorikeets commonly roosted in tall trees with thick trunks and medium density foliage and the trees next to their roost trees were of the same species. Roosting trees were often in areas of high anthropogenic disturbance and close to streetlights."
"Lorikeets chose roost trees that were taller, with thicker trunks and higher first branches than non-roost trees."
"Large flocks of lorikeets preferred to roost in trees that are in contact with another tree"
I'm too lazy to paraphrase, but that just about sums up what a study found regarding Rainbow Lorikeets and how they choose their roosting sites in urban areas. Also here's the suspected reasoning driving such choices;
"Large trees may offer better protection from unfavourable weather and allow birds to perch comfortably (Clergeau and Quenot 2007). Trees with higher first branches may provide protection from predators and allow birds to detect danger quickly (Peh and Sodhi 2002)."
"Large communal roosts may provide the birds with a lower predation risk (Turner and Pitcher 1986)."
"Areas of high disturbances may offer protection from predators which avoid areas of human activity (Peh and Sodhi 2002) and in some cases predation can be reduced in urban environments (Rodewald et al. 2010)."
"A higher detectability of predators may further explain why many roost trees are situated on man-made concrete surfaces, which provide no hiding places for predators. Such surfaces also reflect light and heat, which enhances visibility and provides warmth."
"Lighting along city streets may allow birds to change roosts if needed when threatened, allow for detection of threats (Gorenzel and Salmon 1995) and provide easier orientation to the roost at nightfall, which may maximise the birds’ foraging time"
Source: Jaggard, A. K., Smith, N., Torpy, F. R., & Munro, U. (2014). Rules of the roost: characteristics of nocturnal communal roosts of rainbow lorikeets (Trichoglossus haematodus, Psittacidae) in an urban environment. Urban Ecosystems, 18(2), 489-502.
That is spot on, and very interesting, thanks for that Amateur!
elizabeth
An interesting read Amateur & very insightful. Thanks for the effort you put in.
Good one, Amateur, & most informative.