| I agree: it does apply only to very small distances above the ground or water.
On 18/05/2015, at 4:01 PM, "Philip Veerman" <> wrote: That sounds very interesting, even though I quite don’t understand it. Is it that the resistance against the substrate: ground or water is greater, against than it is in air, from the downbeat of wings. That makes sense although surely this only applies within a very small distance from the surface (no more that a metre or two). Or is it the same as saying air density reduces at higher altitude? But for a pelican that travels largely by thermal soaring, I would have thought there is not much rising thermal air mass less than a metre above a cold water surface like a river. Philip The lower birds fly, the more uplift they obtain (i.e. the less energy required to move horizontally), simply because soil and water are denser than air. There are of course contra-indications which encourage them to take other factors into account!
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I’m unsure as to the intention of the question – location, date, frequency, flying low or over a river and is “Eur” Uriarra? Obviously Pelicans will be flying low when arriving or leaving the water, yes they also fly low some distance over rivers and lakes. I have seen this sometimes at Kambah Pool one flying for several hundred metres (till out of sight) along the river only a metre or two above it. Over places away from water they will usually fly high but that varies, probably according to how much warm air there is. I have an obs from my home on last year’s GBS chart of 3 flying very low over my home.
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