Photo by Steve Zack

Prepared by:Matt Ricketts1 (Matt.Ricketts@lsa-assoc.com), Barbara Kus2 (barbara_kus@usgs.gov), and Bryan Sharp

1 LSA Associates, Inc.
510-236-6810 phone

2 USGS Western Ecological Research Station
San Diego, CA 92123
858-637-6881 phone

RECOMMENDED CITATION

Ricketts, M. and B. Kus. 2000. Yellow-breasted Chat (Icteria virens). In The Riparian Bird Conservation Plan:a strategy for reversing the decline of riparian-associated birds in California. California Partners in Flight. http://www.prbo.org/calpif/htmldocs/riparian_v-2.html

SHORTCUTS

range map

references

SUBSPECIES STATUS:

I. v. virens - breeds from eastern South Dakota to New Hampshire, south to eastern Texas and northern Florida (Pyle 1997).

I. v. auricollis - breeds from southern British Columbia and Saskatchewan to southern California and western Texas, vagrant to Georgia (Pyle 1997).

MANAGEMENT STATUS: California Species of Special Concern

DISTRIBUTION

HISTORICAL BREEDING DISTRIBUTION

Grinnell and Miller (1944) reported that chats bred over the entire length and breadth of the state exclusive of higher mountains and coastal islands, and were more numerous toward the interior.  In migration, chats were similarly widespread, with less restriction as to habitat (dense riparian plant growth).

Sierra Bioregion: Along the west shore of Mono Lake (6400 feet), one or two singing males were present in 1976, 1977, and 1983, but not in intervening or subsequent years.  Although chats are conventionally found in humid thickets, one was observed at Benton Crossing (7000 feet) in sagebrush scrub.  Chats were reported in Benton Crossing from 1980-1990 and in the Yosemite Valley in late September and early October in 1925, 1926, 1928, and 1935 (Gaines 1992). Sacramento Valley Bioregion: In 1973, singing males were common on the Upper Sacramento River in northern Colusa Co., but uncommon on the Feather River from Oroville to Verona (Gaines 1974). San Joaquin Valley Bioregion: Kinsey (1934) found chats nesting near Snelling in Merced Co. Bay/Delta Bioregion: In the San Francisco Bay region, Grinnell and Wythe (1927) described the chat as a “fairly common summer visitant to the warm interior valleys, selecting nesting grounds in willow thickets bordering the lower, sluggish courses of streams.  Chats were reported in summer from San Jose and Agnew (Santa Clara Co.), Hayward and Irvington (Alameda Co.), Lafayette (Contra Costa Co.), Rio Vista (Solono Co.), and Sonoma Co.  Prior to 1944, Kinsey (1945) had encountered chats only three times from July to September “during twenty years of residence and extensive fieldwork in Marin County.”  Kinsey (1934) also captured a hatch-year bird at Manor (near Fairfax) in Marin Co., and he and his wife trapped three males and saw another individual of unknown sex from 23 April to about 14 June 1944 (Kinsey 1945).

CURRENT BREEDING DISTRIBUTION

Expert opinion:

Klamath Bioregion: Yutzy and Yutzy (as reported to Calbird in 1999) reported that chats were “everywhere” in Shasta and Siskiyou Counties. Modoc Bioregion: Small (1994) stated that although breeding status in northeastern California is uncertain, chats probably still breed on the Modoc Plateau and in valleys of the Great Basin in Modoc and Lassen counties. Sacramento Valley Bioregion: Chats have been sighted along the Yolo/Solano Co. lines for the past few years (Hampton, pers.comm.). Bay/Delta Bioregion: From 1997-2002 local birders have reported singing chats at the Santa Rosa Creek flood control channel near the outlet to Delta Pond (approx. ¾ mile west of Willowside Rd., Sonoma Co.) (Shurvinton, pers. obs.). As many as five singing males have been observed at one time (Ricketts and Lictwardt, pers. obs.). Sierra Bioregion: Along the South Fork Valley portion of the Kern River Valley in north-central Kern Co., chats breed in the east to west, cottonwood/red willow-dominated forest found along the lower 14 miles of the South Fork Kern River before its termination at Isabella Reservoir (Barnes 2003). Chats associate with a mulefat understory in this area. An estimated 33-43 pairs were documented during the 2002 breeding season (Barnes 2003). Specific sites where chats were found include: Canebrake Ecological Reserve, Smith Ranch and Onyx Ranch, Kern River Preserve, Sierra Way/Prince's Pond, and South Fork Wildlife Area. South Coast Bioregion: In San Diego County, riparian woodlands of the coastal lowlands, specifically along portions of the San Luis Rey, Santa Margarita, and San Diego Rivers, and along Las Pulgas and Jamul Creeks, contain breeding chats (Unitt 1994).  Reports of chats also exist from the foothills of regions of eastern San Diego County, although these individuals may have been migrants (Unitt 1994).

Point count:

Klamath Bioregion: In 1999, singing chats (n = 70) were recorded at all point count stations in a survey of gravel bars on the lower Eel River in
Humboldt Co. (LBJ Enterprises 1999).  Chats were one of the top 20 most abundant species in each year (1998, 1999) of survey. Sierra Bioregion: 13 individuals were detected over 3 visits in 1999 at Lower Hogback Creek (Inyo Co.) as part of PRBO’s Eastern Sierra Riparian Project (Heath and Ballard 1999). Sacramento Valley Bioregion: Found along the lower Clear Creek Floodway and below Whiskeytown Dam in Shasta Co., Bidwell Park and Oroville Wildlife Area in Butte Co., and Stillwater Park in Glenn Co. (PRBO data, 1998-2002). In Colusa Co., along Little Stony Creek at the East Park Reservoir (Holmes et al. 2000). During the 2000 breeding season chats were detected at the following PRBO point count stations: Haleakala orchard, Kopta Slough, Dye Creek, Battle Creek, La Barranca, Deer Creek (Tehama Co.), BRSP, and Llano Seco (Glenn Co.). Numbers were highest at Dye Creek (n=13) and Battle Creek (n=9), suggesting that tributary streams offer better habitat than mainstream sites. San Joaquin Valley Bioregion: Along the Stanislaus River within the Horseshoe Road Recreation Area (Stanilslaus Co.) and along the Mokelumne River in San Joaquin Co. (PRBO data, 1998).

Mist netting: (female with brood patch, female with eggs in oviduct, juvenile with no skull ossification before 1 August):

Sacramento Valley Bioregion: Nineteen after hatch year (AHY) and 7 hatch year (HY; 1999 only) individuals were captured during three years of breeding season mist netting (1997-1999) along Little Stony Creek in Colusa Co. (Holmes et al. 2000).  During the 2002 season at the Lower Clear Creek Floodway in Shasta Co., the productivity ratio (HY/AHY ratio) for chats was 0.40 at the main study area and 0.27 at Saeltzer Dam (Burnett and DeStaebler 2003).

Nest searching:

Sacramento Valley Bioregion: Four nests were found along Little Stony Creek at the East Park Reservoir over 3 years of nest searching (Holmes
et al. 2000). Six nests were found at Lower Clear Creek in 2002, four of which (67%) fledged young (Burnett and DeStaebler 2003).

Spot mapping:

Sacramento Valley Bioregion: During the 2002 breeding season at the Lower Clear Creek Floodway, 7.50 chat territories were mapped on the Project Area (19 ha) and 9.25 territories were mapped at Saeltzer Dam (15 ha) (Burnett and DeStaebler 2003). Densities at this PRBO study site continued to be higher than at other Sacramento Valley sites (PRBO unpubl. data).

Breeding Bird Atlas:

Bay/Delta Bioregion: Sonoma BBA - Uncommon summer resident. Only confirmed atlas record on Channel Drive near the Annadel State Park parking lot (Parmeter 1995). Marin BBA - Irregular transient and summer resident. In 1982, singing chats were heard from 5 May - 4 June at Laguna Ranch in the Point Reyes National Seashore, and along Walker Creek (~ 1.5 mi. upstream from Hwy. 1) from 1 May - 12 June (Shuford 1993). Central Coast Bioregion: Santa Barbara BBA - Fairly common in the Barka Slough area on Vandenberg A.F.B., along the Santa Ynez River just west of Buellton, and along the upper Santa Ynez River at and above Gibralter Reservoir and along nearby Mono and Agua Caliente creeks (Lehman 1994). Uncommon to fairly common but local summer resident along North Coast, rare transient and summer resident along South Coast. South Coast Bioregion: Orange BBA - Locations where chats were found include: Carbon Canyon Regional Park, Anaheim Wetlands north of Santa Ana River and east of Weir Canyon Rd., Villa Park Dam flood basin, along Skylark Pl. and Presidio Way near Peters Canyon Reservoir, below Rattlesnake Reservoir, Talbert Regional Park (near pond), Big Canyon east of Upper Newport Bay, Sand Canyon Wash above and in Mason Regional Park, San Diego Creek near Irvine Meadows Amphitheater, muleflat near confluence of English and Aliso Creeks (habitat has since been destroyed), Arroyo Trabuco in O’Neill Regional Park, Bell Canyon in Starr Ranch Audubon Sanctuary, and San Juan Creek (see Gallagher 1997 for detailed listing of atlas blocks).  Virtually all birds in Orange Co. were found in mature willows along lowland watercourses (Gallagher 1997).

ECOLOGY

AVERAGE TERRITORY SIZE

In Indiana, Thompson and Nolan (1973) reported mean territory size to be 1.24 ha (range 1.12 – 1.58 ha).  In addition, territory sizes shifted throughout the season; males that arrived early established large territories that shrunk as more males arrived.  They also noted that males will expand their territories if neighboring territories are abandoned (Thompson and Nolan 1973).

TIME OF OCCURRENCE AND SEASONAL MOVEMENTS

Local breeding birds arrive in Santa Barbara Co. in early to mid-April (Lehman 1994).  Breeders in northern populations probably arrive from late April to early May. In Indiana, Thompson and Nolan (1973) noted that males typically arrive earlier than females; the first male usually arrived a week or more before the first female.

Departure from breeding grounds occurs from August – September (after complete prebasic molt); some may leave in July, some stragglers into October. Spring migration: March - May. Fall migration: July - October. Poorly documented due to the species’ secretive nature; it goes largely undetected once singing ceases in mid-July (Dunn and Garrett 1997).

Extent of wintering in California:

Delacour (1959) reported the capture of an adult chat in Los Angeles on 5 December 1958. There are a few winter records from Arcata (Humboldt Co.) to Pasadena (Los Angeles Co.) (Small 1994).

MIGRATION STOPOVER CHARACTERISTICS

No information for California.  However, Dunn and Garrett (1997) report that western birds appear to move south during fall migration on a broad front, although migrants are generally scarcer near the coast.

FOOD HABITS

FORAGING STRATEGY

Foliage gleaning; consumes insects and berries about equally (Ehrlich et al. 1988).

DIET

Nestlings are typically fed a diet of soft-bodied orthopterans (e.g., grasshoppers) and larval lepidopterans (Petrides 1938).  In late summer and fall, chats feed to a large extent on small fruits, such as the fruits of honeysuckle, wild strawberry, blackberry, mulberry, chokecherry, sumac, and nightshade (Dunn and Garrett 1997).

DRINKING

BREEDING HABITAT

In California, chats require dense riparian thickets of willows, vine tangles, and dense brush associated with streams, swampy ground and the borders of small ponds (Small 1994).  Some taller trees (i.e., cottonwoods and alders) are required for song perches (Dunn and Garrett 1997).  Eastern birds can also be found in upland habitats such as old fields.  They are most often found in areas in early stages of succession, as opposed to young and mature forests (Melhop and Lynch 1986).  Annand and Thompson (1997) found chat abundance to be greatest in areas of forests that had been clearcut.  Similarly, Kroodsma (1982) reports that chats preferred brushy areas within powerline corridors to forest edge and interior.  He also found that chats preferred patches with high densities of blackberry vines (Rubus spp.) and tree saplings, while they avoided areas with high percentage grass cover.  Other studies in Missouri (Burhans and Thompson 1999) and Kentucky (Ricketts 1999) confirm chats’ affinity for dense blackberry patches.

NEST SITE FIDELITY

Thompson and Nolan (1973) report low site fidelity in abandoned agricultural fields in southern Indiana.  Only 10% of adult males returned to the site between years, while no adult females and no juvenile birds produced at the site returned.  Males that returned rarely returned to the exact same territory; instead, they tended to move to a nearby territory.  The authors suggest that this low site fidelity may be due to the fact that this study area represents a “sink” habitat.

HEIGHT OF NEST

New Mexico: mean = 1.6 ± 1.2 m (SD) (range 3-6) (USFS RMRS, unpubl. data); Central Texas: mean = 1.21 ± 0.66 m (SE) (Barber and Martin 1997);Kentucky: mean = 78.7  ± 4.1 cm (SE) (Ricketts 1999).

CANOPY COVER

4.1 ± 2.06 (Barber and Martin 1997).

AVERAGE SHRUB COVER

12.06 ± 2.94 (Sedgwick and Knopf 1987).

AVERAGE FORB COVER

35.29 ± 3.77 (Sedgwick and Knopf 1987).

GROUND COVER

19.12 ± 2.95 (Sedgwick and Knopf 1987).

NEST SUBSTRATE

At the Lower Clear Creek Floodway in Shasta Co. most chat nests are found in Himalayan blackberry (Burnett and DeStaebler 2002). Other plant species used for nesting include California blackberry, California wild rose, and pipevine.

On the upper Gila River in southwestern New Mexico, nests (n = 59) were located in the following substrates: Russian-olive (n = 12), box elder (n = 9), Goodding willow (n = 6), coyote willow (n = 6), seep willow (n = 5), canyon grape (n = 4), Virginia creeper (n = 3), Arizona alder, net-leafed hackberry, velvet ash, blue-stem willow (all n = 2), New Mexico Forestiera, 3-leaf sumac, and Siberian elm (1 nest in each).  These nests were in mature riparian forest with proportionately more trees and less shrubs.  In early successional shrubby habitats where chats were even more abundant, the preferred nesting substrates appear to be seepwillow, coyote willow, and canyon grape (USFS RMRS, unpubl. data).

In east-central Kentucky, chats nested in 13 plant species (n = 57 nests), with most in common blackberry (n = 26), multiflora rose (n = 7), and Japanese honeysuckle (n = 5) (Ricketts 1999).

NEST TYPE

Cup;  bulky though well-hidden structure of grasses, dead leaves, and shreds of bark placed about 1 meter above ground; commonly placed in dense patches of wild grape vines of blackberry (Petrides 1938, Dunn and Garrett 1997).

BREEDING BIOLOGY

TYPICAL BREEDING DENSITIES

25 males/km2 in the Sacramento Valley (Gaines 1974); 17-32 males/km2 in Indiana (Thompson and Nolan 1973); 0–3.8 pairs/ha in New Mexico (USFS Rocky Mtn. Research Sta., unpubl. data).

INITIATION OF NESTING

Egg-laying period is from 13 May – 20 July (Thompson and Nolan 1973).

DISPLAYS

Male sings in flight with dangling legs, pumping tail, and slow, deep wingbeats; also flutters above branch while singing. Male’s black mouth lining is sometimes displayed to female, with the male perched below the female, opening his gape fully and moving the body slowly from side to side (Dunn and Garrett 1997).

MATING SYSTEM

Simple monogamy is most common; also successive monogamy and polygyny (Thompson and Nolan 1973).  Successive monogamy occurs most often when a female leaves a male after a failed nest (Thompson and Nolan 1973).

CLUTCH SIZE

Usually 3-4, sometimes 5 (Petrides 1938). In New Mexico, mean clutch size = 4.7 (range 3-6) (USFS RMRS, unpubl. data). In Indiana, mean clutch size = 3.5 (Thompson and Nolan 1973).  Clutches laid early in the egg-laying period tend to have more eggs (usually 4) than clutches initiated later in the egg-laying period (usually 3) (Thompson and Nolan 1973).

INCUBATION

Female

INCUBATION PERIOD

Eleven days; 13 June is earliest initiation date (Petrides 1938).

DEVELOPMENT AT HATCHING

Altricial, no natal down.

NESTLING PERIOD

8 days (Petrides 1938).

PARENTAL CARE

Both sexes tend the young.

POST FLEDGING BEHAVIOR OF OFFSPRING

In the East, Dennis (1967) reports that chats (both juveniles and adults) move north and east into New England and northern parts of the Midwest after the breeding season.  Similar northerly post-breeding, pre-migration movements are not reported for western populations.

NUMBER OF BROODS

Two.

BROOD PARASITISM

Frequent host of Brown-headed Cowbird (Molothrus ater); rare host of Bronzed Cowbird (Molothrus aeneus). Thirty-one percent of chat nests were parasitized by Brown-headed Cowbirds in a 3-year study by Burhans and Thompson (1999) in Missouri. On the upper Gila River in southwestern New Mexico, 32% of chat nests were parasitized (USFS RMRS, unpubl. data). In contrast, of 57 chat nests located in east-central Kentucky, not one nest was parasitized by cowbirds (Ricketts 1999).  The chat is among the 17 hosts most parasitized by cowbirds.  One report of parasitism by a Black-billed Cuckoo (Coccyzus erythopthalmus) in Virginia (Thomas 1995).

Burhans and Freeman (1997) found that chats do have some level of egg recognition, as they rejected about 50% of white-painted  cowbird eggs that were placed in their nests.  They rejected natural cowbird eggs that were experimentally placed in their nests at a much lower rate.  The authors suggest that the difference in rejection rates is due to the degree of egg maculation.

LANDSCAPE FACTORS

ELEVATION

Altitudes for nesting range from near sea level in the Lower Sonoran Life Zone to about 1370 meters through the Upper Sonoran Life Zone, and rarely to 2050 meters (in the White Mtns) (Small 1994).

PATCH SIZE

Burhans and Thompson (1999) found that chats that nested in small patches (average diameter < 5.5 m) that were parasitized by cowbirds experienced higher predation than unparasitized nests in large patches.  However, nests in large patches were also more likely to become parasitized by cowbirds, as were nests with more large stems (> 10 cm dbh) nearby.  Although predation and parasitism appeared to differ across patch sizes, the effects of patch size on host fitness appear to cancel each other out.

DISTURBANCE

Flood control and river channelization eliminates early successional riparian habitat (willow/alder shrub habitats with a dense understory) that chats (and many other riparian focal species) use for breeding.  There is currently no information for California on the possible effects of logging on chat populations, although Annand and Thompson (1997) found chats to be more abundant in forests that had been clearcut in Missouri. Sedgwick and Knopf (1987) report the chat as being sensitive to grazing and suggest that chats and Common Yellowthroats may be good indicator species of the effects of grazing on riparian birds. Chats were commonly found in corridors created within forests for powerlines (Kroodsma 1982).

PESTICIDE USE

No information for California, although Monroe (1978) proposed that pesticide use may be one of the factors responsible for chat population declines in Kentucky.

PREDATORS

Nest predators in Indiana include snakes, Blue Jays (Cyanocitta cristata), and eastern chipmunks (Tamias striatus) (Thompson and Nolan 1973).  In Kentucky, black rat snakes (Elaphe obsoleta) are a primary nest predator, in addition to eastern chipmunks, long-tailed weasels (Mustela frenata), Blue Jays, and American Crows (Corvus brachyrhynchos) (Peake and Ritchison 1998).  Potential nest predators in California include Western Scrub-jays (Aphelocoma californica), dusky-footed woodrats (Neotoma fuscipes), racoons (Procyon lotor), and several species of snakes.

DEMOGRAPHY AND POPULATION TRENDS

DEMOGRAPHICS

Age and sex ratios:
Sex ratio of both breeding and transient chat populations in Indiana did not differ significantly from 1:1 (Thompson and Nolan 1973). Eleven HY/8 AHY birds in one-year of mist-netting at Clear Creek in Shasta Co. (Gardali et al. 1999); 6 HY/15 AHY in 2002 at the Lower Clear Creek Floodway Project Area; 6 HY/22 AHY at Saeltzer Dam (Burnett and DeStaebler 2003).

Productivity measure(s): 1.37 from above data (11/8) (Gardali et al. 1999).

Survivorship:
Information on adult survival is not available. Thompson and Nolan (1973) report low between-year return rates (see ECOLOGY above).  The authors suggest that the low annual return rate may be due to movement to new sites rather than mortality.  However, between and within year survivorship rates are not known.

Reproductive success:
Four of six nests found at the Lower Clear Creek Floodway in 2002 successfully fledged young, yielding a proportional nesting success of 0.67 (Burnett and DeStaebler 2003).

Nineteen percent of nests (all nests initiated, complete and incomplete) were successful (fledged at least one young) in a 5-year study in Indiana (Thompson and Nolan 1973).  A mean of 1.05 fledglings were produced per territory. Of nests receiving eggs, the daily nest survival rate was 93.7%.  Daily egg survival rate was 90.9%, overall hatching rate from 1966-1970 was 28.1%, and the percentage of eggs that produced fledglings was 19.6.  Daily nestling survival rate was 96.4% abd 69.8% of nestlings fledged.  Ninety-three percent of all nest failures were due to predation.  Eighty-nine percent of the nest failures were caused by snakes, Blue Jays, or eastern chipmunks.  Predation and egg removal by cowbirds were responsible for 81% of egg failures, while predation was the cause of all nestling deaths.

Of 49 chat nests found in east-central Kentucky, 22 (45%) were successful and 27 (55%) failed due to predation.  The Mayfield daily survival rate for all nests was 0.96 and mean number of young fledged was 1.4 ± 0.2 fledglings per nest (Ricketts 1999). Of 42 nests of known outcome in New Mexico, only 10 (24%) successfully fledged at least one young.  32% were parasitized by cowbirds, with 1-4 cowbirds eggs per nest.  Most parasitized nests were depredated, but not infrequently chats were able to pull off both cowbirds and their own young (USFS RMRS, unpubl. data)

POPULATION TREND

California BBS data from 1966-1998 shows a nonsignificant increasing trend of 1.1% per year (P = 0.27), along with sub-interval trends of +4.7% (P = 0.18) from 1966-1979 and +0.4% (P = 0.61) from 1980-1999.  However, this data exhibits several deficiencies, including low abundance (less than 1.0 birds/route), low sample size (less than 14 routes), imprecision (3%-year change would not be detected over the long term), and possible inconsistency in trend over time (sub-interval trends were significantly different [P< 0.05] from each other) (Sauer et al. 1999).  BBS data should therefore be interpreted with extreme caution.

MANAGEMENT ISSUES AND OPTIONS

EXOTIC SPECIES INVASION/ENCROACHMENT

Hunter et al. (1988) found that chats will use the exotic saltcedar (Tamarix chinensis), and they suggest that chats may use the saltcedar preferentially to native habitat.  The authors do not report the frequency of nest placement in saltcedar, but Brown and Trosset (1989) report that chats nest in tamarisk and native shrubs in proportion to the occurrence of the different types of vegetation.

Use of Himalayan blackberry (Rubus discolor) as breeding habitat.  Chats have been reported to utilize the exotic Himalayan blackberry in at least one area of California (Zack et al. 1997), and most likely use it throughout the state due to its dense thicket-forming properties.  Any management efforts to remove this plant from riparian areas (ie., exotic removal programs) should first assess any detrimental effects the removal may have on local breeding chats.

MANAGEMENT

Lack of information on location and status of populations in California. Despite many anecdotal reports of areas where chats are abundant, there is very little quantitative data on the location, status, and health of breeding chat populations in California. In particular, riparian forests of the Klamath Bioregion and upper foothill tributaries of the Sacramento River reportedly harbor many chats, but specific information on density, productivity, and nesting success of these populations is lacking.

Potential logging impacts on chat populations in the Klamath Bioregion.  Given that chats are reportedly common in this part of the state and that most of the state’s logging occurs in this area, potential source populations may be in danger from negative logging impacts.  More information is needed on specific breeding distribution in this region, however, before such hypotheses can be tested.

ASSOCIATED SPECIES

Other species that would benefit from early successional riparian habitats with a dense shrub layer include:

Song Sparrow
Common Yellowthroat – found wherever there are chats within PRBO’s riparian sites in the Central Valley (Small, pers. comm.)
Lazuli Bunting
Blue Grosbeak
Willow Flycatcher
Spotted Towhee

MONITORING METHODS AND RESEARCH NEEDS

Establish point count routes in areas where chats have been reported, as well as in regions likely to contain suitable habitat.  Doing so will increase our knowledge of where and at what densities chats breed, along with general habitat associations.

Implement demographic monitoring (mist-netting and/or nest monitoring) at potential reference sites to determine population health (productivity, survivorship, and recruitment) and potential source/sink status.  

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