Birding Puerto Penasco, Sonora, Mexico

Over the last couple of decades, I have spent a lot of time birding in Mexico, amassing a list of over 900 species. At this point, I have only a handful or endemics or near-endemics I need to see and have been spending more time looking for North American migrants, which were not a priority on earlier trips.

One location I have been wanting to visit for some years is Puerto Penasco, which lies on the coast of northern Sonora, only an hour’s drive from the US border. I decided to tack on a couple of days here as part of my Arizona birding trip. Late summer is a pretty bad time to visit due to the high humidity and temperatures, as well as being a poor time for more northerly bird species that sometimes stray down in winter. However, I had a couple of potential “Mexico ticks” that seemed reasonably likely in Common Tern and Baird’s Sandpiper and the visit would give me the opportunity to scout out some areas better. Wes Fritz, who joined me for the Arizona trip, is always keen to explore new areas and was all-in on adding this to the itinerary. Wes provided the photographs for this entry and the next on Puerto Penasco.

After making the hour-long drive from the border crossing, we arrived in Puerto Penasco in mid-afternoon and proceeded to the sewage ponds. The main entrance clearly stated private property and had a guard station, so we decided to see if there were some other points where we could view or access the ponds. After poking around a bit, we found a spot where we could walk in and start birding.

Eared Grebe with "baby on board"

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We were surprised to find several pairs of Eared Grebes with young, since I was not aware this species bred regularly in Sonora or even the adjacent USA. However, a bit of internet sleuthing revealed that Eared Grebes were discovered nesting at these ponds back in 2018, at the time the first occurrence in Sonora. The main purpose of the visit was to look for shorebirds and Black Terns. We found five of the latter and I was able to enjoy their dipping feeding flight. Shorebirds were something of a disappointment due to very limited muddy edges. Other than hundreds of Wilson’s Phalaropes out on the water, we just saw small numbers of most common species. There was no sign of a Baird’s Sandpiper. As we were leaving a couple of kingbirds showed up. The first was a Western but the second was a Tropical, which appears to be fairly unusual in the area. Yellow-footed Gulls were common at the ponds and elsewhere along the coast, with smaller numbers of Ring-billed Gulls and the odd Laughing.

Yellow-footed Gulls

The next morning, we got up early to explore the large estuaries south of town. On the drive down to Puerto Penasco we had had a LeConte’s Thrasher fly across the, so we decided to stop in some suitable habitat on the way to the estuaries. After searching for about 20 minutes, we found a moderately cooperative bird, although it did not allow very close approach.

LeConte's Thrasher

Our first target was the southern spit of the Estero de Morua. Fortunately, the security checkpoints for the various resort communities there had no issue with letting us through and we reached the parking area near the spit. There was a good gathering of terns on the beach right by the carpark, which happily contained eight Common Terns. The estero proved very good for terns, with seven species present. A subsequent visit to the north spit in the afternoon turned up a huge count of 375 Least Terns, along with 64 Black Terns. We walked out around the tip of the south spit, since Baird’s Sandpipers will often feed along the wrack lines of sandy beaches. We had no luck with these but did have an American Oystercatcher and 14 Wilson’s Plovers. The main estero mudflats had a good selection of typical species including a couple of Red Knots, but all were rather distant.

"Frazeri" American Oystercatcher

Least Tern

We then headed further south to the north spit of the Estero de la Pinta. We had less time to explore here and were not inclined to hike the kilometer out to the tip of the sandspit in the heat and humidity. The estuary appeared like the previous one in terms of species, although almost all the mudflats were covered by the high tide. We found a promising-looking vagrant trap at the entrance to the Vidante resort. There were singles of Yellow Warbler and Western Wood-pewee there.

A return trip to the sewage ponds yielded nothing new except over 30 Lesser Nighthawks. We ran into the security guard who told us we had to leave, vindicating the previous day’s decision to “ask for forgiveness, not permission”!