Peregrine Status & Monitoring

The Peregrine Falcon was removed from the Federal Endangered and Threatened Species List in August of 1999. Outlined as a requirement for removal, a monitoring plan was developed and is currently in affect.

If populations were again to decline, the species would be reinstated.  Each individual state also maintains an Endangered and Threatened Species List. The Field Museum’s Chicago Peregrine Program monitors our Illinois Peregrines. Monitoring is critical for evaluating population viability and recovery.

The Peregrine Program’s goal is to have a self-sustaining population of breeding falcons that is at a low risk (less than 1%) of statewide extirpation. With current population levels, we are well on our way to achieving this goal.


For northern Illinois, the peregrine nesting season begins with courtship in late winter (Feb-March) until fledging of young in mid summer.You may see some Peregrines with bands on their legs.  These are unique to the individual and allow us document where an individual bird has gone if read.  It's important that if you see a Peregrine, try to get as much information on the bands as possible.  Which legs have a band? What color(s)? Letters and/or numbers and orientation?  In the graphic to the left, you see some possible color band combinations.  How do read this?  Bottom row has 4 possible color bands, all being a black over red band.  This first band I would write as b/r A/B.  The following would be b/r 98/A, third band as b/r 6/*D, and last as b/r *P/*H.

While the majority of time monitoring peregrines centers around breeding activities, we are also interested in migration and wintering behaviours.  People should feel free to email Mary Hennen with peregrine observations or questions at any time of the year.   If you would like read about Stephanie Ware's experiences helping with the Chicago Peregrine Program, check out her personal peregrine blog at erinyes

Our seasonal activities are outlined below.

COURTSHIP -late Jan through March The adult peregrines are once again seen togther in courtship activities. Aerial behaviours include hunting together, food transfers, and flight displays.  The adults are defensive of the natal territories.  Male peregrines will form a scrape to entice females.  Our monitoring efforts focus on trying to locate new sites by looking for pairs of peregrines in new locations.  It is also when we are likely to witnesses terriorial fights with new peregrines trying to get into an established site.

EGG LAYING - late March to early April One egg is laid every 24-48 hours.  Incubation does not fully commence until the clutch is nearly complete.  A typical clutch is 3-4 eggs.

INCUBATION - April to mid May The length of incubation is usually 30-32 days.  Male peregrines will assist but more so during the early stages.  This time period is one of the best for trying to identify the adult peregrines.  Females will usually stay on or directly near the eggs which give us the opportunity to try and read her leg bands.  If we approach the nest while the male is incubating, he will usually get off the eggs and the female will fly in.  Some males perch nearby will allow us to try and see his bands.  While we have a fair number of unbanded adults, we sometimes have the opportunity to confirm of it's the same bird year and after through the genetics of the offspring. 

HATCHING - mid may For the Chicago area peregrines, hatching usually begins around Mother's Day (how appropriate.)  Females will brood the chicks for the first week.  This is the time period where the adults are most defensive of the natal site.  Male peregrines will be hunting for the female and chicks.  By surveying the ground below the nest ledge, monitors are able to examine prey remains and see what species the falcons are feeding upon. 

BANDING Banding takes place when the chicks are around 21-24 days old.  Physically the birds are as large as they are going to get, only the flight feathers have not grown in.  So we can place bands on the legs and not worry about the birds out-growing the bands.  The bands are unique to the individual this scientists are able to study longevity and dispersal.   Not all nests are accessible so some birds go unbanded.

FLEDGING - mid June to July A peregrine's first flight is generally a glide down to another level.  Occasionally that means the ground.  In the city, if they land on the street, we will make sure they are ok and if so, return them to the nest.  Usually the seond attempt at flight goes fine.  It is the scariest time of the year for the peregrine watchers - to see where the young fly to.  The Chicago Peregrine Program is indebted to the many individuals who keep track of each site and watch to make sure the young peregriens are safe.  Please check out the 'In Case of Emergency' portion of the website.

MIGRATION / WINTERING Through reports on banded peregrines, we have been able to see that most of adults stay for the winter.  Territories may shift to different area.  For instance, we know that the Uptown peregrines often like to hangout at Montrose Harbor during the non breeding season.  Though we try for the most part to allow the peregrines to breed without human assistance in any manner, some of our peregrines are using nest boxes.  This off season is when we would make repairs if needed.