desertdharma said:One local had even reported to her that they saw a hummer in the ant guard water, taking a little splash. I wonder if that's true?!
MBP said:While hummingbirds definetely seem to love bathing, I do not think they need to drink any. Since the nectar they consume contains about 75 % water, and given the amount of intake every day, they problem tends to be too much water already by simply feeding. Nectar-feeding animals need specially designed kidneys to handle this challenge. A study in broad-billed hummingbirds has shown that they are able to turn they kidneys completely off in the night, so they do not dehydrate, since these organs are made to turn over huge amounts of water (well, from a hummingbird's perspective ).
MBP said:While hummingbirds definetely seem to love bathing, I do not think they need to drink any. Since the nectar they consume contains about 75 % water, and given the amount of intake every day, they problem tends to be too much water already by simply feeding. Nectar-feeding animals need specially designed kidneys to handle this challenge. A study in broad-billed hummingbirds has shown that they are able to turn they kidneys completely off in the night, so they do not dehydrate, since these organs are made to turn over huge amounts of water (well, from a hummingbird's perspective ).
High rates of nectar intake by hummingbirds can
necessitate excretion of substantial amounts of excess
water (Beuchat, Calder & Braun, 1990), so the kidneys
must be capable of rapidly processing large volumes of
very dilute urine. Calder & Hiebert (1983) have measured
osmolalities of urine samples collected from birds
in the field and noted that they were typically very dilute
(<100 mOsm), although they did measure some urine
samples that were probably isosmotic or even slightly
hyperosmotic (reported in Beuchat et al., 1990). The
concentrations of electrolytes in the urine of the birds
(4±19 mM Na+, 10±27 mM K+) mirror the low electrolyte
levels typical of the nectar produced by hummingbird-
pollinated plant species (Baker & Baker, 1975;
Hiebert & Calder, 1983).
Despite the high rates of fluid intake by hummingbirds,
there are environmental situations in which the
birds must deal with potential dehydration. Rates of
evaporative water loss in these small birds are very high,
even at modest ambient temperatures (Lasiewski, 1964;
Powers, 1992), and the amount of nectar required for
energy balance can be inadequate to maintain positive
water balance (Calder, 1979). In these circumstances,
hummingbirds must be able to minimize urinary water
loss through renal or post-renal mechanisms.