Editing Cliff swallow (section)

== Behavior ==
Cliff swallows live in a colonial lifestyle during the breeding season, composed of a large number of pairs per nesting site.<ref name=":2" /><ref name=":1" /><ref name=":7" /> This group-style life can present the birds with some benefits and disadvantages; valuable information can be shared through group learning about food location and [[habitat]] preferences, but it is also much easier to transmit parasites or [[disease]]s when living in close proximity.<ref name=":2" /><ref name=":1" /><ref name=":12">{{Cite journal|last1=Brown|first1=Charles R.|last2=Brown|first2=Mary Bomberger|date=2015-02-01|title=Ectoparasitism shortens the breeding season in a colonial bird|journal=Royal Society Open Science|language=en|volume=2|issue=2|pages=140508|doi=10.1098/rsos.140508|pmid=26064606|issn=2054-5703|pmc=4448812|bibcode=2015RSOS....240508B}}</ref> The cliff swallows have an unusually large parasite community that includes [[Parasitism|ectoparasites]], ticks, [[flea]]s and swallow bugs, among others.<ref name=":2" /><ref name=":1" /><ref name=":7" /><ref name=":12" /><ref name=":13">{{Cite journal|last1=Brown|first1=Charles R.|last2=Roche|first2=Erin A.|last3=O’Brien|first3=Valerie A.|date=2015-02-01|title=Costs and benefits of late nesting in cliff swallows|journal=Oecologia|language=en|volume=177|issue=2|pages=413–421|doi=10.1007/s00442-014-3095-3|pmid=25266478|bibcode=2015Oecol.177..413B|s2cid=13863210|issn=0029-8549}}</ref> These parasite [[infestation]]s have been shown to negatively affect juvenile growth and developmental rates.<ref name=":0" /><ref name=":12" /><ref name=":13" />

Cliff swallows are socially [[Monogamy in animals|monogamous]], one pair will look after each nest, but many occurrences of [[Animal sexual behaviour#Polygamy|sexual polygamy]] have been noted because of the varying [[genetics]] throughout the colony and within many individual nests.<ref name=":2" /> Both the female and the male cliff swallows will contribute to the colony's genetic variability by performing various actions of [[brood parasitism]].<ref name=":2" /><ref name=":1" /><ref name=":4" /><ref name=":8">{{Cite journal|last1=Brown|first1=Charles R.|last2=Brown|first2=Mary B.|date=2004|title=Mark–Recapture and Behavioral Ecology: a Case Study of Cliff Swallows|journal=Animal Biodiversity and Conservation|volume=27|issue=1|pages=23–34|doi=10.32800/abc.2004.27.0023 |doi-access=free}}</ref> The cliff swallows have an "aggressive and fearless" personality in comparison to their relatives the barn swallows, who were noted as being "timid and fearful".<ref name=":1" />

=== Diet ===
[[File:In-flight_and_Mid-air_feeding_of_juvenile_cliff_swallow_by_an_adult.jpg|thumb|239x239px|In-flight and mid-air feeding of juvenile cliff swallow by an adult]]
The cliff swallows feed on a diet consisting of [[Pterygota|flying insects]], particularly swarming species such as: flies, bees, lacewings, mayflies, butterflies, moths, grasshoppers, and damselflies.<ref name=":1" /><ref name=":7" /> The birds forage high (usually 50 m or higher) over fields or [[marsh]]es, and tend to rely on bodies of water like ponds during bad weather with high winds.<ref name=":2" /><ref name=":1" /> These birds are day-hunters ([[Diurnality|diurnal]]), returning to their nesting sites at [[dusk]], and are not very active during cold or rainy weather because of the low number of prey available.<ref name=":1" /><ref name=":0" /> [[Foraging]] behaviors related closely to their [[Reproduction|reproduction cycle]]; when the birds first arrive at the nesting site they will forage as far as 10 miles from the colony, in the hopes of increasing body fat reserves to prepare for cold-windy days and their energy extensive egg-laying stage.<ref name=":2" /><ref name=":1" /> When the swallows return to the nesting site at dusk, they often fly in a tightly coordinated flock overhead, in such close [[synchronization]] that they may appear as one large organism.<ref name=":1" /><ref name=":7" /> These large group formations are called creches.<ref name=":7" />

The cliff swallows' social behavior does not end with these "synchronized flying" displays; they use special vocalizations to advise other colony members of a good prey location where ample food is available.<ref name=":1" /> It has been thought that colony sites located close to marshes would have larger quantities of insects to support big populations; however, there are equally large nesting colonies located at a great distance from marshes.<ref name=":1" />

=== Vocalisations ===
{{Birdsong|url=http://www.xeno-canto.org/species/Petrochelidon-pyrrhonota|species=American cliff swallow}}The social structure of these cliff swallow colonies has evolved a complex [[Bird vocalization|vocalisation]] system.<ref name=":2" /><ref name=":1" /><ref name=":7" /> Five vocalisations have been identified, which are used by both juveniles and adults for different reasons.<ref name=":2" /> These vocalisations are structurally similar across the age groups and can be described as begging, alarm, recognition, and squeak calls, all with some variations.<ref name=":2" /> Juvenile cliff swallows are said to have established a unique call by the approximate age of 15 days, which allows the parents to identify their chick from others in the colony.<ref name=":2" /><ref name=":1" />

The "squeak" call is of great interest to researchers because this is the special vocalisation made at a distance from the colony when a bird encounters a good foraging area.<ref name=":1" /> When this call is heard, large groups of their colony "neighbours" will arrive at the location.<ref name=":1" /> This "squeak" call is used greatly during bad weather conditions.<ref name=":2" /><ref name=":1" /> For this specific call, the cliff swallows are one of the few known [[vertebrate]]s to make a "competitively disadvantageous" cue to their peers for food availability.<ref name=":1" />

Alarm calls are heard at the colony while the birds are flying over and around the colony entrance way, and serve as a signal of danger close to the nests. When this call is heard by the other colony members, a mass fleeing of birds out and away from their nests is observed.<ref name=":1" />
[[File:American_Cliff_Swallows,_PE_Cty.jpg|right|thumb|Collecting mud at a puddle, [[Prince Edward Point]], [[Ontario]]]]

=== Reproduction ===
The breeding season of cliff swallows starts with the return of the birds from their wintering grounds. They usually arrive in large groups and start immediately to choose their nesting sites.<ref name=":2" /><ref name=":1" /> The cliff swallows have been observed to skip from one to five years between breeding at the same place to avoid parasite infestations, but some pairs will return annually to the same site.<ref name=":1" /> Particularly for younger pairs, the size of the colony can affect their reproductive success, because they seem to rely on the valuable information that can be obtained from a large colony.<ref name=":2" /><ref name=":1" /> Older birds are usually found in smaller colonies and exhibit earlier nesting times, avoiding the parasite manifestation that comes with the hot mid-summer season.<ref name=":1" /><ref name=":12" /><ref name=":13" />

[[File:Cliff_Swallow_(5946633586).jpg|right|thumb|Mate delivering food to cliff swallow nest]]
Cliff swallows decide upon arrival at their nesting site whether they will fix a nest from the previous season or build a new nest.<ref name=":2" /><ref name=":1" /> Building a new nest may have the benefit of lower parasite numbers, but it is very energy expensive and time-consuming.<ref name=":1" /><ref name=":13" /> Further, taking the extra time to build a nest from scratch will mean reproducing later which could negatively affect their chicks' survival.<ref name=":2" /><ref name=":1" /><ref name=":13" /> Nests constructed with [[Clay|sticky clay]] can last a number of years and are further supported by the cliff swallows' tier-stacking construction strategy.<ref name=":2" /><ref name=":1" /><ref name=":7" /> Cliff swallows from the same colony [[social]]ly collect mud for nest building, being seen converging at small areas together and then carrying globs of mud in their bills back to their nests.<ref name=":1" />

Each bird pair will have about 3–4 nestlings per brood; a clutch size of 4 has been identified as the most common and most successful.<ref name=":8" /> The cliff swallows brood-parasitize neighboring nests, where the females may move their eggs into or lay their eggs in other nests.<ref name=":2" /><ref name=":7" /> The females who show intra-specific parasitism tend to have greater reproductive success than those that were brood-parasitized.<ref name=":2" /><ref name=":8" /> The "victims" of brood-parasitism must nurture more chicks with higher energy costs and decreased [[Fitness (biology)|fitness]] because they are raising young that will not pass on their own genetic material.<ref name=":8" /> The male cliff swallows will also take part in this gene-spread by mating with more than just one female, contributing to genetic variation throughout the colony.<ref name=":2" />
[[File:Swallow_nest_occupied_by_House_Sparrow.jpg|left|thumb|A cliff swallow nest occupied by a house sparrow]]
The nesting sites can be vulnerable to [[predation]] by other cavity-nesting bird species, such as the [[house sparrow]].<ref name=":1" /><ref name=":7" /> These birds will search a number of swallow nests for the perfect place to make their own nest, destroying numerous eggs in the process.<ref name=":1" />  Nests, especially those at the periphery of colonies, are vulnerable to snake predation.  Central nests are more coveted, have larger clutches, and are preferred for reuse in subsequent years <ref>{{Cite journal |last1=Osborne |first1=S. |last2=Leasure |first2=D. |last3=Huang |first3=S. |last4=Kannan |first4=Ragupathy |date=2017-01-01 |title=Central Nests are Heavier and Have Larger Clutches than Peripheral Nests in Cliff Swallow (Petrochelidon pyrrohonota) Colonies |url=https://scholarworks.uark.edu/jaas/vol71/iss1/36 |journal=Journal of the Arkansas Academy of Science |volume=71 |issue=1 |pages=206–208 |doi=10.54119/jaas.2017.7132 |s2cid=52210939 |issn=2326-0491|doi-access=free }}</ref>
[[File:2006.06.22_cliff_swallow_egg_from_end_of_San_Luis_Drain,_CA_009i.jpg|right|thumb|Cliff swallow egg]]
Once the house sparrows pick their nest, they will bring in grass and other materials making it impossible for the cliff swallows to re-establish their place.<ref name=":2" /><ref name=":9">{{Cite journal|last1=Leasure|first1=Douglas R.|last2=Kannan|first2=Ragupathy|last3=James|first3=Douglas A.|date=2010|title=House Sparrows Associated with Reduced Cliff Swallow Nesting Success|jstor=40600386|journal=The Wilson Journal of Ornithology|volume=122|issue=1|pages=135–138|doi=10.1676/09-061.1|s2cid=85866560}}</ref> Thus, the colonies with house sparrow predation have an overall lower success rate and fewer previous-year nests being used.<ref name=":9" />

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