We continue to suffer from incomplete reporting from professionals working at places such as offshore islands and the Guerrero Negro saltworks. Publication of some records has been actively suppressed. Another concern is that records that appear in eBird may be subsequently removed. Ours remains an imperfect reporting system!

Table 1. Summary of naturally occurring species recorded on the Baja California Peninsula in 2023.

	Baja California Peninsula	Baja California	Baja California Sur
Total Species Recorded	414	378	341
Rare and Uncommon Species1 Unreported	Ainley’s Storm-Petrel, Buller’s Shearwater, Townsend’s Shearwater, Long-eared Owl, Guadalupe Junco, Sagebrush Sparrow	Yellow-billed Cuckoo, Xantus’s Hummingbird, Elf Owl, Bronzed Cowbird, Indigo Bunting	Scripps’s Murrelet, Guadalupe Murrelet

¹   as defined in the spreadsheet attached to this report

Abbreviations: BC (Baja California); BCS (Baja California Sur); Mcp. (municipio); I. (Isla); ph. (photograph); † (description).

Geese through Shorebirds

There was little to highlight among goose observations in 2023. On the down side, Brant was unrecorded south of Bahía Magdalena and only one Cackling Goose was found in BC. Three widely scattered Wood Ducks made for a better than average showing, with singles at Campo Mosqueda 26 Jan (†Amy McAndrews, Jorge Montejo, Ricardo Guerra), Ensenada 12 Oct–2 Nov (ph. E. D. Zamora-Hernández et al.), and Pescadero 13 May (ph. Glenn Ehrenberg); the latter establishing the first La Paz Mcp. record. Other ducks rarely reported in BCS included Mallards at the Guerrero Negro saltworks 25 Nov (Víctor O. Ayala-Pérez et al.) and Estero San José (up to two 12 Nov–29 Dec; ph. Víctor O. Ayala-Pérez, ph. Jedidiah Smith et al.); Canvasbacks at the Guerrero Negro saltworks 26 Nov (Víctor O. Ayala-Pérez et al.), Loreto 29 Dec 2022–24 Feb (ph. Bill Levine, ph. Claudia S. Huergo et al.), and around La Ribera (up to three, 24 Dec 2022–15 Jan; †Jane Seward, ph. Roberto Pineda et al.); Hooded Mergansers at San Ignacio 18 Feb–15 Mar (ph. R. A. Erickson et al.) and Loreto 22 Feb–6 Mar (ph. Gary Martindale et al.); and a Common Merganser at the Guerrero Negro saltworks 25 Nov (†Víctor O. Ayala-Pérez et al.), just the second documented for the state. A cooperative Harlequin Duck at Rosarito 22 Jul–29 Sep (ph. L. Q. Kahle et al.) was seen by many and established the sixth regional record. Five Black Scoters and two White-winged Scoters were all on the Pacific coast from Bahía San Quintín north.

A Red-necked Grebe at Estero Punta Banda 16 Dec–10 Jan 2024 (†Nick A. Lethaby, ph. Celic Montoya et al.) established the fifth regional record, but followed two in 2022. A Ruddy Ground-Dove near Punta Colonet 6 Oct (†Nick A. Lethaby) was the only one found north of southern BCS and established the first record for the reduced Ensenada Mcp (Figure 1). Up to five Groove-billed Anis remained at Estero San José through the year, and one was present in La Paz 15–29 Apr (ph. Stefanny Villagómez et al.). Black Swift is probably a rare but regular spring migrant through northern BC, but there are very few records. One in the Sierra San Pedro Mártir 15 May (ph. J. Vargas, Mark L. Hoffman) was the first to be photo documented in the region, and only the third seen in >20 years. Nine Broad-billed Hummingbirds in BCS included five on the Vizcaíno Peninsula in Oct (ph. L. Q. Kahle). Two were found in BC, in Ensenada Mcp.: Valle La Misión 13 Oct (ph. L. Q. Kahle) and Maneadero 25 Oct–12 Nov (audio, †Ángela Tamayo Vázquez). However, the hummingbird highlight of the year was the Violet-crowned Hummingbird at Valle La Misión 8 Apr–mid Jul and mid Aug– 30 Aug (ph. Lawrence S. Beck et al.; photo at North American Birds 75: 53), the first to be documented in the region.

For the fifteenth consecutive year, a mixed pair of a Black Oystercatcher and an American Oystercatcher was present on the gulf coast in the Punta Arena de La Ventana area, this time 15 Feb–4 Apr (†Gary J. Strachan, ph. Thea Ulen et al.). The only American Golden-Plover seen was at Estero Punta Banda 28 Sep (ph. J. Vargas et al.), where it established the first documented record for Ensenada Mcp. Three Pacific Golden-Plovers were found: San Antonio del Mar 3 Oct (ph. R. A. Erickson; first for Tijuana Mcp.); Lagunita El Ciprés 30 Oct (ph. E. D. Zamora-Hernández); and Guerrero Negro 15 Dec (ph. Sergio Alcalá). Rarer still in northwestern BC was the Wilson’s Plover at Lagunita El Ciprés 28 Mar (ph. †J. Vargas, ph. Álvaro San José). No Mountain Plovers were found, as has been the case most years since 2017. Most notable among Scolopacid observations was a Ruff seen by many at La Paz 10 Oct–10 Mar 2024 (ph. Jorge Cristerna et al.). A Stilt Sandpiper was at Estero Punta Banda 5–7 Oct (†Nick A. Lethaby) and six more were in BCS. Birds outside their typical seasonal windows included a Dunlin at Lagunita El Ciprés 2 Jun (ph. E. D. Zamora-Hernández) and a Baird’s Sandpiper at La Paz 9 May (ph. Nathan French).

Alcids through Falcons

Exceptional alcid records were of a Pigeon Guillemot at Bajamar 16 Jul (ph. René Valdes, Nit Pineda; first for Ensenada Mcp.) and an Ancient Murrelet on the Gulf of California near Bahía de los Ángeles 17–18 Jun (†Brooks Hart, ph. Kemp Anderson; photo at North American Birds 75: 64).

At least nine Laughing Gulls along the Pacific coast from Bahía San Quintín north 12 Nov–9 Feb 2024 were far more than usual. Four Franklin’s Gulls in about the southern third of the peninsula from 25 Oct onward was also more than usual. Two were found on the Pacific coast in spring. One last species well represented late in 2023 was Short-billed Gull; seven were located on the coast from Lagunita El Ciprés north and one was all the way south at Estero San José 31 Dec (ph. Efraín Octavio Aguilar Pérez). A Yellow-footed Gull at Rosarito 12 Nov (ph. Celic Montoya, Alonso Sánchez) was most unexpected, as there is only one previous record for the Pacific coast of BC north of the Guerrero Negro area. Only two Lesser Black-backed Gulls were found: Bahía de Magdalena 20 Feb (ph. Doug Gochfeld et al.; first for Comondú Mcp.) and Lagunita El Ciprés 2 Sep (ph. J. Vargas, ph. Antonio Maldonado). Arctic Tern made a rare onshore appearance at Bahía Magdalena 12 Oct (ph. J. Vargas, Graciela Tiburcio Pintos); there are few records for BCS.

A Wedge-rumped Storm-Petrel was ca. 55 km west-southwest of Bahía Asunción 18 Aug (ph. John King). The only regional record farther north, and the only one for BC, is from I. Guadalupe 31 Jan 1950 (Auk 69: 460–461). First state records (for BCS and BC, respectively) were established by a Wilson’s Storm-Petrel off Bahía Magdalena 12 Oct (ph. J. Vargas, Graciela Tiburcio Pintos) and a Wedge-tailed Shearwater ca. 35 km southwest of Punta San Carlos 19 Sep (†Scott B. Terrill, ph. Linda S. Terrill).

An adult Wood Stork at Presa Rodríguez, Tijuana 26 Mar (ph. J. Vargas et al.) and 13 Dec–19 Feb 2024 (ph. R. A. Erickson, ph. L. Q. Kahle) established the first record for Tijuana Mcp. and is believed to be the same individual seen at various locations around southwestern California since at least 2020 (McCaskie and Garrett 2023a; McCaskie and Garrett 2023b; McCaskie and Garrett 2023c). Similarly, an adult at La Paz 19 Jan–7 Feb (ph. Javier Eduardo Alcalá Santoyo, Jeremiah Trimble) is believed to be the same bird wandering around the Cape Region since 2017. Another bird, mid-peninsula at San Ignacio 19 Mar (ph. Enrique Flores García, Jesús Atondo; first Mulegé Mcp. record), had no such known history.

Neotropic Cormorant consolidated gains in northern BC, with first records for Tijuana (one at Parque de la Amistad 16–26 Mar, ph. Amelia Fallon et al.; and up to eight at Presa Rodríguez 22 Mar–24 Jul, †L. Q. Kahle, ph. R. A. Erickson et al.) and Tecate (one at Ciénega Redonda 4 Apr, ph. R. A. Erickson, †L. Q. Kahle) Mcps. Between the border municipios and the Cape Region, there remains a single satisfactory record: two at Bahía San Luis Gonzaga, BC, 1–3 Apr 2015 (North American Birds 69: 497).

American and Least Bitterns were reported only from the far north and the far south of the region. One or two Tricolored Herons in the Río Colorado delta 5 May (†Benito Rocha Brambila) represented one of few records for the Colorado Desert portion of the region. Numbers of Western Cattle Egrets in the region have declined, and the species is now primarily limited to the Mexicali Valley and the Cape Region.

The ever-enigmatic White-tailed Kite remained true to form; only three were reported south of the Ensenada region. An observation sure to be coveted by many readers was of a Swallow-tailed Kite at San Juan de los Planes 1 May (ph. Edgar Becerril), the second ever found in the region. Another fabulous kettle of hawks seen over San José del Cabo 4–5 Dec included an estimated 20 Broad-winged Hawks and 20 Swainson’s Hawks along with a few Turkey Vultures and Zone-tailed and Red-tailed Hawks (ph. Janice Wenarchuk). The search for the first (Cape) Northern Pygmy-Owl nest came to an end at San Dionisio 14–28 May (ph. Osiel Alejandro Flores Rosas). Details are to be published separately. Three Short-eared Owls at Laguna San Ignacio 20 Jan (ph. Abril Heredia, Daniel Galindo Espinosa) and one at Mesa de la Choya 26 Nov (ph. Víctor O. Ayala Pérez et al.) were the only ones seen. Burrowing Owls visited ships off southwestern BC 11 Oct and well east of San José del Cabo 17 Oct (both ph. Nigel Milius, Wendy Hare), as did two American Kestrels approximately 90 km west-northwest of Cabo San Lázaro 6 Oct (ph. Noam Markus).

Hurricanes Hilary and Norma

Two major hurricanes hit our region in 2023. Hurricane Hilary formed southwest of Oaxaca, reaching hurricane status far offshore Jalisco. On the evening of 20 Aug, Hilary made landfall around San Quintín, then made its way northward and eastward into the Mohave Desert (McCaskie and Garrett 2023). Coverage of this hurricane was limited in Mexico, in part due to road conditions. Hurricane Norma formed roughly far offshore Guatemala, and became a hurricane around offshore Guerrero. On 22 Oct, Norma made landfall around Los Cabos and proceeded northward up through La Paz before cutting eastward across the Gulf of California to mainland Mexico. Data collection was again limited, but large numbers of storm-driven seabirds were found around La Paz.

The effects of Hilary were noted toward the northern end of the peninsula, especially in interior regions around Ensenada, Tijuana, and Tecate. The majority of birds noted displaced by the storm were Least Storm-Petrels, followed by Black Terns, and a variety of shorebirds (Table 2). Least Storm-Petrels were noted on three inland reservoirs. To the north, birds displaced by the storm were noted inland to southern California, Nevada, and Arizona. Given the number of birds found in the southwestern United States, it is clear that better coverage in Baja California, including the Mexicali Valley, would have produced many additional unusual sightings. Southbound birds, possibly heading back to desired feeding grounds after being displaced by the storm, noted far to the south at Punta Arena, BCS 23 Aug included a mix of storm-petrels, shearwaters, and a Cook’s Petrel (G. Marrón).

Observations following Hurricane Norma centered around La Paz, 22–23 Oct. This hurricane was stronger on landfall, and produced more sightings of displaced seabirds than did Hilary. The majority of birds were again storm-petrels (primarily Leach’s and Wedge-rumped), but there were also many Black Terns, Red-footed Boobies, Wedge-tailed Shearwaters, Red Phalaropes, and other species (Table 3). The majority of sightings came from inside La Paz Bay, where birds appeared to be “trapped,” although displaced seabirds were also noted nearby at Presa de la Buena Mujer and Punta Arena Ventana.

During both hurricanes, the day immediately after impact was the peak for observations of storm-blown birds and large, accessible bodies of water such as reservoirs, harbors and bays produced the lion’s share of sightings.

Table 2. Selected waterbird observations following passage of Tropical Storm (former Hurricane) Hilary, Aug 2023; at Presa Emilio López Zamora, Ensenada, 20–21 Aug (E. D. Zamora-Hernández, J. Vargas, Antonio Maldonado) and in Tijuana and Tecate Municipios 21 Aug (R. A. Erickson).

Location; Date	Presa Emilio López Zamora 20 Aug	Presa Emilio López Zamora 21 Aug	Presa Rodríguez 21 Aug	Presa Las Auras 21 Aug	Presa El Carrizo 21 Aug	Ciénega Redonda 21 Aug
Species
Short-billed Dowitcher					1
Red-necked Phalarope	20				15
Lesser Yellowlegs					1
Black Tern					2
Common Tern	1
Least Storm-Petrel	3		2		1

Table 3. Selected waterbird observations in the La Paz area following passage of Hurricane Norma, Oct 2023 (L. Q. Kahle). Species seen on 22 and 23 Oct are indicated by a slash separating the number seen on each date. Other entries are for 22 Oct only.

Species/Location	La Paz Bay	Lagunas de Oxidación	Presa Buena Mujer	Punta Arena la Ventana
Red Phalarope	120/0	3/1	1
Red-necked Phalarope	45/0	180/65		2
Long-tailed Jaeger	3/0
Parasitic Jaeger	7/0
Large jaeger/skua sp*	0/1
Sabine’s Gull	110/10			3
Sooty Tern	1/0
Least Tern	18/3	2/0		2
Black Tern	41/1	200/15	30	4
Common Tern	2/0	1/0
Red-billed Tropicbird	1/0
Leach’s Storm-Petrel**	30/0			8
Wedge-rumped Storm-Petrel	30/3	1***/0		8
Black Storm-Petrel	4/0
Least Storm-Petrel****	6/20			7
Storm-Petrel sp.	35/150
Wedge-tailed Shearwater	200/0			230
Red-footed Booby	140/0		1***	25

* probably a South Polar Skua, but not identified with certainty

** the much less-likely Townsend’s Storm-Petrel not necessarily eliminated

*** seen overhead, and not necessarily associated with surface water

**** dwindling light meant that many individuals remained unidentified, though most were thought to be Least Storm-Petrels

Flycatchers through Finches

The only previous regional Greater Pewee record was from the unexpected location of Mexicali. Even less expected was one in the Sierra Juárez at Laguna Hanson 4 Oct (ph. J. Vargas, ph. R. A. Erickson). Several nearby mountain records north of the border all come from summer. Most California records are from the immediate coast, so future records may be expected from Ensenada, Tijuana, or similar areas. The only two Hammond’s Flycatchers reported were in the Mexicali Valley in spring, where the species is most regular. Dusky Flycatcher was not reported from the Mexicali Valley or the breeding grounds in the Sierra San Pedro Mártir; the only one found was in the Sierra de La Laguna 15 Jan (†G. Marrón), where extremely rare. The only Eastern Phoebe found was also in the Cape Region, near Santiago 30 Jan (ph. Roberto Pineda). Only four Tropical Kingbirds were found in BC during the fall vagrant season. Most notable were three birds in spring north of Cape Region nesting areas: Guerrero Negro 20 May (ph. Sara Alcalá Jiménez), San Ignacio 29 May (†Jesús Atondo), and Loreto 25 May (ph. Tom Haglund). An Eastern Kingbird at Guerrero Negro 17 May (ph. Sara Alcalá Jiménez) established just the fourth spring record for the peninsula, and the sixth all-time for BCS. Scissor-tailed Flycatcher was represented by a single bird at Cabo San Lucas 25 Mar (ph. Joaquín Corrales).

Bell’s Vireos were again found on the Río Colorado in Nov, suggesting the species might regularly winter there; two were at Laguna Grande 18 Nov (L. Q. Kahle). Nominate Bell’s Vireos have been well represented in the region, and particularly on the Vizcaíno Peninsula, in comparison to adjacent states and provinces. Suitingly, two were located this fall: 19 Oct at Rancho San José de Castro (†) and 29 Oct at Guerrero Negro (ph.)(both L. Q. Kahle). Plumbeous Vireo had an above-average showing in BC and northern BCS. One in the Sierra Juárez 4 Oct (J. Vargas, R. A. Erickson) was at an unusual montane locality. Clark’s Nutcrackers irrupted throughout the western United States in 2023 and up to four were in the Sierra San Pedro Mártir 21 Sep–20 Feb 2024 (José Hiram Licona Hernández, ph. Gus Hawk et al.).

A pair of Tree Swallows brought feather lining to a nest hole in a willow snag on the Río Tijuana, west of Tecate, 17 May (ph. R. A. Erickson). Details of the only previous state and national nesting record known to us have been suppressed by the observers. The number of swallows wintering in the Cape Region varies year to year. Fifteen hundred Tree Swallows were near Ciudad Insurgentes 17 Jan (Sue Carnahan, Curtis Smith), but otherwise the species was found in low numbers in the winters of 2023 and 2024. The maximum Barn Swallow estimates were of 900 at Estero San José 5 Jan (Gautam Apte et al.) and only 50 at La Paz 22 Oct (L. Q. Kahle). Single Bank Swallows were at La Paz 17 Feb (Alex Lamoreaux et al.) and 23 Oct (L. Q. Kahle). Few Purple Martins were reported from BC. A Wrentit was at El Rosario 15 Oct (ph. L. Q. Kahle). The species’ range once extended to Misión San Fernando, but we are unaware of any other sightings as far south as El Rosario since 2004.

Red-breasted Nuthatch underwent a major irruption up and down the west coast of North America this fall (McCaskie and Garrett 2023). The first one reported in BC was on I. Guadalupe 13 Sep (†Jessica Vázquez). Highlights of subsequent observations included the first for Mexicali Mcp., at Ejido Johnson 20 Sep (†José Juan Butrón Rodríguez); high counts of five at Bajamar 1 Oct (Kurt A. Radamaker, J. Vargas), six near Punta Colonet 6 Oct (Nick A. Lethaby), and seven at El Rosario 31 Oct (L. Q. Kahle); and one in BCS at Bahía Asunción 26 Oct (ph. L. Q. Kahle). A Brown Creeper near El Salto 15 Jan (ph. Álvaro San José) was part of an earlier irruption by that species in the southwestern United States in winter 2022–2023. More unusual than the Gray Catbirds in fall (Table 4) was one in the Sierra de San Francisco 27 Jan (ph. Eduardo Fernández Reza). And more unusual still was a Brown Thrasher at Ejido Nuevo Rosarito 30 Oct (ph. L. Q. Kahle), establishing just the third and southernmost regional record.

The winter of 2022–23 was an extraordinary one for Mountain Bluebird, with concentrations peaking toward the second half of the season. Notable were 200 at Ojos Negros 18 Feb (Kurt A. Radamaker) and 120 north of Camalú 30 Jan (Amy McAndrews, Jorge Montejo), the former establishing a high count for the peninsula. Two Townsend’s Solitaires were in BCS, in the Sierra de San Francisco 24 Feb (ph. G. Marrón). In BC, two away from the mountains, at Ojos Negros 29 Jan and San Telmo 31 Jan (both Amy McAndrews, Jorge Montejo), were likewise noteworthy. Swainson’s Thrush is rarely reported south of northern BCS; one at Ramaditas 24 Oct (ph. L. Q. Kahle) was the first recorded for Comondú Mcp. The major movement of migratory American Robins (Turdus migratorius propinquus) that “brought record high numbers south to San Diego and Imperial Counties” early in the year (McCaskie and Garrett 2022) extended south to our region. Unprecedented numbers were found in BCS, with high counts of up to 15 at San Ignacio 15–19 Mar (ph. Enrique Flores García et al.) and eight near Nopoló 21 Feb (ph. Gary Martindale, Paul Heady, Jonny Wahl). The southernmost recorded was on I. San José 8 Jan (Shayne Sanders).

Our region outdid its northern neighbors with regards to Red-throated Pipit, with ten noted between San Quintín and the Vizcaíno Peninsula 23 Oct–1 Nov (L. Q. Kahle). In contrast, only three others were found on the west coast of North America south of Alaska this fall. Red Crossbills were found only in the Sierra San Pedro Mártir, in Apr, Sep, and Dec. Unfortunately, none were audio recorded. Fall 2023 through winter 2024 was exceptional for a variety of call types in California and western North America. Birders in the mountains of BC should be sure to audio record any crossbills encountered to analyze for types other than the expected Type 2. The movements of Purple and Cassin’s Finches in the region are not well understood, and have changed over time; certainly unusual, though, were flocks of 60 Cassin’s in the Sierra Juárez at Rancho Ramona 19 Feb (†Roberto Pineda); and 29 Cassin’s away from montane habitat at Héroes de la Independencia 31 Jan and 11 Purples at Rancho Ciénega Redonda 28 Jan (both ph. Amy McAndrews, Jorge Montejo). Cassin’s Finch was not reported anywhere during the second half of the year! American Goldfinches were not widespread this year, but one at Presa Emilio López Zamora, Ensenada, and six at Presa Rodríguez, Tijuana (both 24 Jul, L. Q. Kahle), were in suitable breeding habitat and could be indicators of local nesting.

Table 4.  Selected vagrant passerines on the Baja California Peninsula 22 Sep– 20 Nov 2023. Many more birds were seen in Nov 2023 than in Nov 2022. Unrecorded altogether during this season were Least Flycatcher, Eastern Phoebe, Philadelphia Vireo, and numerous warblers (Virginia’s, Hooded, Bay-breasted, Black-throated Blue, Yellow-throated, Prairie, Grace’s, Black-throated Green, and Canada).

Species	Baja California	Baja California Sur
Red-eyed Vireo	1	1
Yellow-green Vireo	1
Gray Catbird	2
Brown Thrasher	1
Bobolink	1
Orchard Oriole	6	1
Baltimore Oriole	1	1
Ovenbird	1
Prothonotary Warbler	1
Tennessee Warbler	2	2
Lucy’s Warbler		2
Cape May Warbler		1
Northern Parula	4	1
Magnolia Warbler		1
Blackburnian Warbler	4	1
Chestnut-sided Warbler	2	1
Blackpoll Warbler	3	1
Palm Warbler	1	5
Pine Warbler	1
Painted Redstart	2
Scarlet Tanager	1
Rose-breasted Grosbeak	2
Indigo Bunting		1
Painted Bunting	1	2
Dickcissel	2
Total	38	21

Longspurs through Dickcissel

An impressive list of landbird migrants tallied during 6 hours at sea off northwestern BC 26 Apr included three Mourning Doves, one Anna’s Hummingbird, one Rufous/Allen’s Hummingbird, one Yellow-breasted Chat, and numerous warblers: eight Orange-crowned, five Nashville, one MacGillivray’s, six Yellow-rumped, two Townsend’s, and eight Wilson’s (Gerry and Linda Baade).

Longspurs were present in somewhat above-average numbers this fall, with five Chestnut-collareds and six Laplands located, all in BC. Most were at traditional locations of Villa Jesús María and El Socorro (all L. Q. Kahle). A Grasshopper Sparrow at Bahía Tortugas 27 Oct (L. Q. Kahle) was a rare fall migrant and one just north of the state line near Guerrero Negro 16 Jan (†Sara Alcalá Jiménez) was the only other one reported. Golden-crowned Sparrow had a notably poor fall all along the west coast of North America, and only two were seen in BC in the second half of the year. A Harris’s Sparrow in Tijuana 19 Mar–9 Apr (ph. Jack Crawford et al.) represented only the third peninsular record, though remarkably the second for poorly-covered Tijuana Mcp. (the first pertaining to a bird seen on the border fence 20 Dec 1969). Two White-throated Sparrows were seen early in the year, one lingering until 14 Apr in Tijuana (ph. Amelia Fallon et al.), but only one was found in the fall.

Nelson’s Sparrow is a scarce and local winter resident in coastal salt marshes the length of (Alta) California. As such, wintering populations have been expected in the salt marshes of Bahía San Quintín, Guerrero Negro, and other localities for years, though efforts to locate this secretive and enigmatic species have been few and far between. Two found 14 Dec on the shores of Bahía San Quintín (†Nick A. Lethaby) at a logical (and pre-scouted) high-tide roost established just the second record there (first in 1961), where the species may well winter annually. Up to three birds were seen there later in the season by many observers, with the last report of a single bird 24 Feb 2024 (ph. Sean Rovito). Swamp Sparrows had a notably poor year on the peninsula, with just one lingering wintering bird through 11 Feb in Ensenada (ph. I. Raymundo-González et al.) and none in fall. Green-tailed Towhees were present in much larger than typical numbers on the Vizcaíno Desert in fall, a trend noted through much of the western North American deserts (L. Q. Kahle).

Yellow-headed Blackbird was recorded in fall in above average numbers on much of the peninsula; 250 at El Rosario 30 Oct (L. Q. Kahle) was the highest count away from the Mexicali Valley. As in recent years, at least three Orchard Orioles wintered at Estero San José. Three more were found in winter at three locations north to San Ignacio. Three Bullock’s Orioles were noted in BCS, two in the Vizcaíno Desert in fall and one in the Cape Region in Feb. Reversing the pattern, one Baltimore Oriole was found in the Vizcaíno Desert in fall and two were in the Cape Region in Jan and Feb. Red-winged Blackbird is very rare on about the middle two thirds of the peninsula; the species was not seen in that region in 2023 except at Loreto. Tricolored Blackbirds nested successfully at traditional locations in Tecate Mcp.: Rancho Ciénega Redonda and Ejido José María Pino Suárez. At least 100 birds enjoyed a prolonged nesting period at the former site (4 Apr–28 Jul) but fewer than 10 adults were at the latter 17 May (R. A. Erickson et al.). Two hundred birds were initially prospecting at Rancho Ciénega Redonda 4 Apr and singles and groups of up to 15 were seen elsewhere during the year, south as far as Rancho Meling, in the foothills of the Sierra San Pedro Mártir. Another blackbird with declining numbers in the region is Bronzed Cowbird. It went unrecorded altogether in the Mexicali Valley in 2023; the only one found was at Todos Santos 26 Nov (†Mick Griffin). A Great-tailed Grackle at Los Cabos 4 Sep (ph. David H. Gleit) was the only one reported south of the Vizcaíno Desert.

Fall warbler highlights were fewer and farther between than in some years (Table 4). Most notable were Prothonotary Warbler in Ensenada 2–4 Nov (†J. Vargas, ph. Yuriko Kuwabara et al.), Cape May Warbler at San Carlos 25 Oct (ph. L. Q. Kahle), and Pine Warbler at La Salina 3 Nov (ph. L. Q. Kahle). Two or more Painted Redstarts were at El Rosario in Oct (ph. L. Q. Kahle et al.), surprisingly the first recorded at this warbler-rich locality.

Winter warblers were better represented. Highlights in BC included Northern Parula on the Río Colorado at Laguna Grande 18 Nov (likely a returning bird) (ph. L. Q. Kahle), Chestnut-sided Warbler at Presa Rodríguez 13 Dec–8 Feb 2024 (ph. R. A. Erickson, L. Q. Kahle), Pine Warbler in Tijuana 26 Mar (ph. †J. Vargas, Antonio Maldonado), and returning Townsend’s x Black-throated Green Warbler hybrid at El Rosario 15–31 Oct (ph. L. Q. Kahle). In BCS north of the Cape Region, a Cape May Warbler was on the Magdalena Plain at Ramaditas 24 Oct–6 Feb 2024 (ph. L. Q. Kahle, ph. R. A. Erickson) and a returning Prairie Warbler was at Guerrero Negro 7 Dec 2022–26 Mar (ph. Sara Alcalá Jiménez et al.). But wintering species in the Cape Region were most impressive, and included (the now annual) Louisiana Waterthrush, Tennessee Warbler, and Lucy’s Warbler. More notable were Mourning Warbler near El Campamento 20 Jan (†Steven G. Mlodinow) and a nice selection from the Sierra de La Laguna: Virginia’s Warbler 14 Jan (†Steven G. Mlodinow), Hooded Warbler for its third winter at San Dionisio 18 Dec 2022–20 Feb (ph. Osiel Alejandro Flores Rosas), two Yellow-throated Warblers, Grace’s Warbler 17 Jan (†Steven G. Mlodinow), Black-throated Green Warbler 9 Dec (ph. †James Bailey), and two Painted Redstarts. A Belding’s Yellowthroat at Punta Conejo 24 Mar (†Gary J. Strachan) was at a new location, but not in typical habitat.

It was a good spring for Summer Tanagers in the western United States, and a bird at Rosarito 22–24 Jul (†L. Q. Kahle, J. Vargas) may well have been overflow from spring. Hepatic Tanager is not annual on the peninsula, with most records coming from the coast from the Ensenada region north in winter. One at Punta Banda 21 Nov–13 Dec (ph. L. Q. Kahle, †Nick A. Lethaby) could not have been at a more typical date and location. Exceptional was a male Scarlet Tanager near La Paz 14 Jun (Adriana Miranda Torres, ph. Levi Arellano Huerta), representing the first spring record for the peninsula. A Varied Bunting at Oasis del Edén 19 Oct (ph. L. Q. Kahle) established the fourth record for extreme northwestern BCS. One of the two Dickcissels this fall was at the gulfshore locality of Bahía de los Ángeles 5 Oct (ph. George and Mary Flicker).

Rancho Ciénega Redonda Tricolored Blackbird Nesting Colony Acoustic Monitoring

The Tricolored Blackbird nesting colony at Rancho Ciénega Redonda was acoustically monitored for the second consecutive year. Wendy Schackwitz performs data analysis and wrote the following summary for 2023.

Tricolored Blackbirds have a rich repertoire of vocalizations specific to various breeding stages, enabling the ability to determine the onset of each breeding stage through documenting the timing of associated vocalizations (Schackwitz et al 2020, Honig and Schackwitz 2023, Beedy et al. 2023). The five breeding phases and their associated vocalizations are: settlement (male chorus and female chatter); incubation (female chatter with lack of male chorus); brooding (hatchling and nestling calls); fledging/creche formation (fledgling calls); and dispersal (sudden reduction in fledgling calls) (Beedy et al. 2023). To determine the timing of the breeding stages of the colony, R. A. Erickson deployed an AudioMoth Autonomous Recording Unit (ARU) adjacent to the colony 14 Apr–22 Aug. The ARU was programmed to record one minute of audio every 20 minutes resulting in 9352 recordings. After retrieving the ARU, we used the software online service Automated Remote Biodiversity Monitoring Network (Arbimon, Rainforest Connection, Katy, Texas, United States of America) for acoustic analysis of six focal blackbird vocalizations: male song, male chorus, female song, and begging calls from hatchlings, nestlings, and fledglings (Honig and Schackwitz 2023). Onset of breeding stages was then assigned based on the presence and absence of these six vocalizations. To determine colony behavior, and avoid tracking single individuals that are outliers, we require that there be at least three detections of a vocalization in a day to indicate presence of a breeding stage.

Vocalizations were extremely faint in the audio recordings, confounding analysis, with only two of the six vocalizations (male chorus and fledgling call) detected reliably. Three bouts of male chorus were detected (14 April–1 May, 22 May–2 Jun, and 19–24 Jun) and three bouts of fledgling calls (1–6 May, 24 May–5 Jun, and 21–24 Jun). Given that incubation is approximately 11 days, and brooding approximately 14 days, the fact fledglings were heard only 17 days after initiation of recording suggests that the recorder was placed during the first bout of incubation. The first bout of fledgling calls was followed 23 days later by a second, which in turn was followed 28 days later by a third, suggesting that there were three bouts of breeding, each of which successfully fledged young. The last bout of male chorus (19–24 Jun) was followed by a few intermittent fledgling calls, and we cannot be certain if these were from a small fourth bout of breeding, or if perhaps lingering fledglings from the previous bouts.

Programa de Aves Urbanas (PAU)

The Programa de Aves Urbanas (PAU) is a citizen science project promoted by Mexico’s Comisión Nacional para el Conocimiento y Uso de la Biodiversidad (CONABIO) in collaboration with the Cornell Lab of Ornithology and Environment for the Americas. There are six working groups on the peninsula: Ensenada and San Quintín in BC; and Guerrero Negro, Cabo Pulmo, San Antonio, and La Paz in BCS. PAU has been operating in the city of Ensenada since 2018. The program includes a set of projects whose main objective is to promote interest and citizen participation in birdwatching and provide recreational options for people living in cities, while simultaneously helping them learn more about urban birds. PAU–Ensenada has focused on identifying local groups dedicated to birdwatching, with the aim of joining forces and forming a network of local birders that promote birdwatching in different sectors within the community. The object is for participants to support each other to collect quality data that helps protect birds and their habitats. Currently PAU-Ensenada involves the Instituto de Planeación Ambiental y Calidad de Vida, A.C. as coordinator, and ProEsteros, A.C, Los Correcaminos birdwatching club, Observatorio Guadalupe, and Contacto Salvaje as trainers.

Motus Wildlife Tracking System

The Motus wildlife tracking system, launched by Birds Canada in 2014, will greatly enhance our understanding of bird movement. According to the Motus website, by using a network of widely distributed coordinated receiving stations (usually towers), “an international collaborative network of researchers uses automated radio telemetry to simultaneously track hundreds [thousands?] of individuals of numerous species of birds, bats, and insects.” When fully implemented and functional, this system will allow the efficient and affordable tracking of innumerable individual birds and other organisms across the globe.

Beginning in 2021 and extending through 2023, twelve Motus stations have been placed along nearly the length of the Baja California Peninsula, seven in BC and five in BCS. These are all overseen by Julián García Walther, who is associated with Pronatura Noroeste, A.C. and the University of Massachusetts, Amherst. Thus far, stations are primarily associated with wetland sites. While the technology is still new, some interesting findings have already emerged. Motus is primarily project-based, and much of the data to date has come from a few targeted initiatives that have put tags on birds in western North America. Regardless, the ability to detect certain species, including those that are quite cryptic in migration, will allow for a massive advancement in our understanding.

Two examples of information already collected follow. Swainson’s Thrush, a relatively scarce migrant throughout the peninsula and normally thought of as very scarce in the Cape District, was detected by Motus three times in BCS, and twice in La Paz. The most complete account is of a bird first banded on 29 Aug 2022 in southwest British Columbia, and subsequently recorded that year in south-coastal Oregon 23 Sep, I. San Jeronimo 24 Sep, and finally at Guerrero Negro 25 Sep (motus 41876). In spring, a Red Knot tagged on the Gulf of California in northwestern Sonora on 24 Apr 2023 was recorded later in the year in Apr and May elsewhere on the coast of Sonora, along the Río Colorado, BC, at the Salton Sea, California, in western Nevada, and coastal Washington, before being recorded in coastal southern Alaska 16–18 May. The bird returned to coastal Sonora by 22 Jul 2023 (motus 45888).

Like all technologies, especially in their infancy, Motus comes with some challenges. Not the least of which is false positives. At least 23 species, including some as unrealistic as Brown-capped Rosy-Finch, appear to have been detected in error in BC. However, these were all tied to a single location in Quebec on a single date, and undoubtedly involved a technology error. The remainder of the peninsular records appear to be accurate. What causes this sort of misfire isn’t currently well known, but this technology is sure to vastly improve in future years and decades.

Preliminary Status Codes for the States and Municipios of the Baja California Peninsula

We have updated the list of all species recorded in each of the municipios on the peninsula, and season and abundance codes for all (spreadsheet 2.5MB PDF). Species recorded in each municipio in 2023 are indicated. The same information is shown for Baja California, Baja California Sur, and for the two states combined. The newly established San Felipe Mcp. is included for the first time (Figure 1). Such recent geographic changes are not yet incorporated into the eBird reporting system. Kurt Radamaker continues to offer an online GIS version of the new map where users can zoom in on areas of particular interest to them.

Although we continue to make progress, the spreadsheet remains preliminary. As we explained last year, although we have tried for consistent treatment in all situations, inconsistencies are bound to be present. Downscaling state status codes to the municipio level is problematic. Although a species may be labeled as rare for the state (“rare, but annual or nearly so”) and be distributed equally throughout the state, it becomes harder to reach the nearly annual threshold in smaller regions such as municipios. And the municipios themselves vary greatly in size. Additional issues in creating–and maintaining–the spreadsheet were discussed in last year’s report.

We expect future editions of this spreadsheet to include various subspecific entries, e.g., “Oregon” and “Slate-colored” Dark-eyed Juncos and more. Adding accurate nesting codes for each municipio will be hard, but it is our long-term goal.

Limited observer coverage best explained several odd patterns in this year’s bird records. Forty-three naturally occurring species and four exotic species were recorded in all 12 municipios in 2023. These included such expected species as Mourning Dove, Turkey Vulture, Red-tailed Hawk, Common Raven, House Finch, White-crowned Sparrow, Orange-crowned Warbler, and Yellow-rumped Warbler, but also a few surprises such as Red-necked Phalarope, Bonaparte’s Gull, Common Loon, Merlin, and Black-throated Gray Warbler.

Shading

Shaded cells indicate species recorded in that state or municipio during 2023.

Darker shading indicates species recorded for the first time in that area in 2023.

Codes

We abbreviate Baja California Peninsula as BCP, Baja California as BC, and Baja California Sur as BCS. The codes used follow Erickson et al. (2013. Erickson, R. A., R. Carmona, G. Ruiz-Campos, M. J. Iliff, and M. J. Billings. Annotated Checklist of the birds of Baja California and Baja California Sur, second edition. North American Birds 66: 582–613.), which were modified from Howell et al. (2001; Howell, S. N. G., R. A. Erickson, R. A. Hamilton, and M. A. Patten. An annotated checklist of the birds of Baja California and Baja California Sur, pages 171–203 in: Birds of the Baja California Peninsula: Status, Distribution, and Taxonomy. Monographs in Field Ornithology No. 3.).

Abundance Codes

c common

u uncommon

r rare, but annual or nearly so

vr very rare: less than annual but more than five records

x extremely rare: five or fewer records

esc. records only involve birds judged to be escapees by eBird definition

Seasonal Codes

R confirmed or presumed breeding resident

S breeding summer resident

W winter visitor

T transient migrant in spring and fall

Sp spring transient migrant; depending upon the species involved, this period may begin as early as January or end as late as July

F fall transient migrant; depending upon the species involved, this period may begin as early as June or end as late as December

V non-breeding visitor; present up to all year (mainly seabirds)

[ ] use of brackets indicates former status, generally >40 years ago for species now considered historical only, but may be as few as 10–12 years for declining species

Breeding Codes (used at state level and above only)

* confirmed breeding species: nests, eggs, dependent young (except some waterbirds, e.g., begging juvenile terns, which may travel with adults for hundreds of km), adults nest building (except woodpeckers, wrens, and Verdin, which may drill/build roost nests), adult(s) carrying food/fecal sac, adults entering nest cavity, birds collected in breeding condition by reliable collectors (cf. Binford, L. C. 1989. A distributional survey of the birds of the Mexican state of Oaxaca. Ornithological Monographs 43: 68).

*? probable breeding: adult(s) singing, courting, displaying, territorial and/or agitated as if nest and/or young nearby, in season and in range/habitat

+ possible breeding: adult(s) in season in range/habitat

( ) irregular and/or former (confirmed, probable, or possible) breeding, e.g., waterbirds dependent on ephemeral water conditions

[ ] former (confirmed, probable, or possible) breeding, i.e., species considered extirpated or extinct

Documentation Codes (used at state level and above only)

S unqualified sight record

SP sight record published with adequate supporting documentation

S! sight record; written documentation archived (cf. Hamilton, R. A. and S. N. G. Howell. 2001. Log of bird record documentation archived at the San Diego Natural History Museum, pages 242–253 in: Birds of the Baja California Peninsula: Status, Distribution, and Taxonomy. Monographs in Field Ornithology No. 3. )

SoP sonogram published

PP identifiable photographic record published, includes stills captured from video tape

# specimen record, including eggs

Acknowledgments

In addition to the observers cited above, we wish to thank the following individuals for uncited observations or other assistance provided during the year: Alejandra Calvo Fonseca, Michael D. Carmody, Nadine de Jong, Horacio de la Cueva, Michael P. Force, Peter A. Gaede, José Emer García, Kimball L. Garrett, Robert A. Hamilton, Adriana Hernández Álvarez, Steve N. G. Howell, Marshall J. Iliff, Paul E. Lehman, Marco Antonio Martínez Damián, Jimmy McMorran, Robert J. Meese, Eric Mellink, Anny Peralta-García, Peter Pyle, J. Van Remsen, Michael L. P. Retter, Gary H. Rosenberg, Wendy Schackwitz, Thomas S. Schulenberg, Eduardo Soto Montoya, Brian L. Sullivan, Philip Unitt, Jorge Valdez Villavicencio. Hamilton and Howell also made many improvements to the text.

Report processed by Andrew Keaveney, 25 Jul 2024.