Editing Hummingbird (section)

===Hemoglobin adaptation to altitude===

Dozens of hummingbird species live year-round in tropical mountain habitats at high altitudes, such as in the Andes over ranges of {{Convert|1500|m|ft}} to {{Convert|5200|m|ft}} where the [[Blood gas tension|partial pressure of oxygen]] in the air is reduced, a condition of [[hypoxia (medical)|hypoxic challenge]] for the high metabolic demands of hummingbirds.<ref name="projecto">{{Cite journal |last1=Projecto-Garcia |first1=Joana |last2=Natarajan |first2=Chandrasekhar |last3=Moriyama |first3=Hideaki |last4=Weber |first4=Roy E. |last5=Fago |first5=Angela |last6=Cheviron |first6=Zachary A. |last7=Dudley |first7=Robert |last8=McGuire |first8=Jimmy A. |last9=Witt |first9=Christopher C. |last10=Storz |first10=Jay F. |display-authors=3 |date=2013-12-02 |title=Repeated elevational transitions in hemoglobin function during the evolution of Andean hummingbirds |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=110 |issue=51 |pages=20669–20674 |bibcode=2013PNAS..11020669P |doi=10.1073/pnas.1315456110 |issn=0027-8424 |pmc=3870697 |pmid=24297909 |doi-access=free}}</ref><ref name="guardian">{{Cite news |date=13 December 2013 |title=How do hummingbirds thrive in the Andes? |work=The Guardian |url=https://www.theguardian.com/science/grrlscientist/2013/dec/13/grrlscientist-hummingbirds-andes-hemoglobin-evolution |access-date=15 August 2022}}</ref><ref name="Lim">{{Cite journal |last1=Lim |first1=Marisa C.W. |last2=Witt |first2=Christopher C. |last3=Graham |first3=Catherine H. |last4=Dávalos |first4=Liliana M. |date=2019-05-22 |title=Parallel molecular evolution in pathways, genes, and sites in high-elevation hummingbirds revealed by comparative transcriptomics |journal=Genome Biology and Evolution |volume=11 |issue=6 |pages=1573–1585 |doi=10.1093/gbe/evz101 |issn=1759-6653 |pmc=6553505 |pmid=31114863}}</ref> In Andean hummingbirds living at high elevations, researchers found that the oxygen-carrying protein in blood {{Ndash}} [[hemoglobin]] {{Ndash}} had increased oxygen-[[Ligand (biochemistry)|binding affinity]], and that this adaptive effect likely resulted from evolutionary [[mutation]]s within the hemoglobin molecule via specific amino acid changes due to natural selection.<ref name=projecto/><ref name=guardian/><ref name="gayman">{{Cite web |first=Deann|last=Gayman |date=2 December 2013 |title=New study reveals how hummingbirds evolved to fly at high altitude |url=https://news.unl.edu/newsrooms/today/article/new-study-reveals-how-hummingbirds-evolved-to-fly-at-high-altitude |access-date=15 August 2022 |publisher=Department of Communication and Marketing, University of Nebraska-Lincoln}}</ref>