Editing Hummingbird (section)

=== Kidney function ===

The dynamic range of metabolic rates in hummingbirds<ref>{{Cite journal |last1=Suarez |first1=R.K. |last2=Gass |first2=C.L. |year=2002 |title=Hummingbirds foraging and the relation between bioenergetics and behavior |journal=Comparative Biochemistry and Physiology |series=Part A |volume=133 |issue=2 |pages=335–343 |doi=10.1016/S1095-6433(02)00165-4 |pmid=12208304}}</ref> requires a parallel dynamic range in [[kidney]] function.<ref name="Bakken et al">{{Cite journal |last1=Bakken |first1=B.H. |last2=McWhorter |first2=T.J. |last3=Tsahar |first3=E. |last4=Martinez del Rio |first4=C. |year=2004 |title=Hummingbirds arrest their kidneys at night: diel variation in glomerular filtration rate in Selasphorus platycercus |journal=The Journal of Experimental Biology |volume=207 |issue=25 |pages=4383–391 |doi=10.1242/jeb.01238 |pmid=15557024 |doi-access=free|bibcode=2004JExpB.207.4383B |hdl=2440/55466 |hdl-access=free }}</ref> During a day of nectar consumption with a corresponding high water intake that may total five times the body weight per day, hummingbird kidneys process water via [[renal function|glomerular filtration rates]] (GFR) in amounts proportional to water consumption, thereby avoiding [[water intoxication|overhydration]].<ref name="Bakken et al"/><ref name="ajp">{{Cite journal |last1=Bakken |first1=B.H. |last2=Sabat |first2=P. |year=2006 |title=Gastrointestinal and renal responses to water intake in the green-backed firecrown (Sephanoides sephanoides), a South American hummingbird |journal=AJP: Regulatory, Integrative and Comparative Physiology |volume=291 |issue=3 |pages=R830–836 |doi=10.1152/ajpregu.00137.2006 |pmid=16614056 |hdl-access=free |s2cid=2391784 |hdl=10533/177203}}</ref> During brief periods of water deprivation, however, such as in nighttime torpor, GFR drops to zero, preserving body water.<ref name="Bakken et al"/><ref name="ajp"/>

Hummingbird kidneys also have a unique ability to control the levels of [[electrolyte]]s after consuming nectars with high amounts of [[sodium]] and [[chloride]] or none, indicating that kidney and glomerular structures must be highly specialized for variations in nectar [[Mineral (nutrient)|mineral]] quality.<ref>{{Cite journal |last1=Lotz |first1=Chris N. |last2=Martínez Del Rio |first2=Carlos |year=2004 |title=The ability of rufous hummingbirds ''Selasphorus rufus'' to dilute and concentrate urine |journal=Journal of Avian Biology |volume=35 |pages=54–62 |doi=10.1111/j.0908-8857.2004.03083.x}}</ref> Morphological studies on Anna's hummingbird kidneys showed adaptations of high [[capillary]] density in close proximity to [[nephron]]s, allowing for precise regulation of water and electrolytes.<ref name="ajp"/><ref>{{Cite journal |author1=Beuchat, C.A. |author2=Preest, M.R. |author3=Braun, E.J. |year=1999 |title=Glomerular and medullary architecture in the kidney of Anna's Hummingbird |journal=Journal of Morphology |volume=240 |issue=2 |pages=95–100 |doi=10.1002/(sici)1097-4687(199905)240:2<95::aid-jmor1>3.0.co;2-u |pmid=29847878 |s2cid=44156688}}</ref>