Editing Peregrine falcon (section)

===Decline due to pesticides===
The peregrine falcon became an endangered species over much of its range because of the use of [[organochlorine pesticide]]s, especially [[DDT]], during the 1950s, '60s, and '70s.<ref name=Cade1988/> Pesticide [[biomagnification]] caused [[organochlorine]] to build up in the falcons' fat tissues, reducing the amount of calcium in their eggshells. With thinner shells, fewer falcon eggs survived until hatching.<ref name=Ehrlich1992/><ref name=Brown1976/> In addition, the PCB concentrations found in these falcons are dependent upon the age of the falcon. While high levels are still found in young birds (only a few months old) and even higher concentrations are found in more mature falcons, with levels peaking in adult peregrine falcons.<ref name=":0">{{cite journal |last1=Risebrough |first1=R. W. |last2=Rieche |first2=P. |last3=Peakall |first3=D. B. |last4=Herman |first4=S. G. |last5=Kirven |first5=M. N. |title=Polychlorinated Biphenyls in the Global Ecosystem |journal=Nature |date=December 1968 |volume=220 |issue=5172 |pages=1098–1102 |doi=10.1038/2201098a0 |pmid=5723605 |bibcode=1968Natur.220.1098R |s2cid=4148056 }}</ref> These pesticides caused falcon prey to also have thinner eggshells (one example of prey being the black petrels).<ref name=":0" /> In several parts of the world, such as the eastern [[United States]] and [[Belgium]], this species became [[local extinction|locally extinct]] as a result.<ref name=Snow1998/> An alternate point of view is that populations in eastern North America had vanished due to hunting and egg collection.<ref name=Lehr2000/> Following the ban of organochlorine pesticides, the reproductive success of Peregrines increased in Scotland in terms of territory occupancy and breeding success, although spatial variation in recovery rates indicate that in some areas Peregrines were also impacted by other factors such as persecution.<ref>{{cite journal |last1=McGrady |first1=Michael J. |last2=Hines |first2=James E. |last3=Rollie |first3=Chris J. |last4=Smith |first4=George D. |last5=Morton |first5=Elise R. |last6=Moore |first6=Jennifer F. |last7=Mearns |first7=Richard M. |last8=Newton |first8=Ian |last9=Murillo-García |first9=Oscar E. |last10=Oli |first10=Madan K. |title=Territory occupancy and breeding success of Peregrine Falcons Falco peregrinus at various stages of population recovery |journal=Ibis |date=April 2017 |volume=159 |issue=2 |pages=285–296 |doi=10.1111/ibi.12443 |bibcode=2017Ibis..159..285M |url=http://nora.nerc.ac.uk/id/eprint/516720/1/N516720PP.pdf }}</ref>